Chapter 12Chapter 12

Inheritance Inheritance Patterns & Human Patterns & Human

GeneticsGenetics

Bellwork: Complete with Bellwork: Complete with your partner on the white your partner on the white boardboard

The synthesis of polypeptides from the genetic The synthesis of polypeptides from the genetic information encoded in mRNA isinformation encoded in mRNA is A. TranscriptionA. Transcription B.TranslationB.Translation C. TransposonC. Transposon D. DNA MethylationD. DNA Methylation

At the end of DNA replication, each of the At the end of DNA replication, each of the daughter molecules has one old strand and daughter molecules has one old strand and one new strand. This explains why DNA one new strand. This explains why DNA replication is described as _____________.replication is described as _____________.

Chromosomes & InheritanceChromosomes & Inheritance

A.A. Thomas Hunt Morgan- early 1900’sThomas Hunt Morgan- early 1900’s-experiments with -experiments with fruit fliesfruit flies

-observed -observed 4 pairs of chromosomes4 pairs of chromosomes

-noticed that 3 pairs were the same in -noticed that 3 pairs were the same in males & females but that 1 pair was males & females but that 1 pair was different. different.

- called these - called these “sex chromosomes”.“sex chromosomes”.

Autosomes & Sex ChromosomesAutosomes & Sex Chromosomes

Sex chromosomes-Sex chromosomes- contain genes that contain genes that determine the gender of an individual.determine the gender of an individual.

Autosomes-Autosomes- the remaining pairs of the remaining pairs of chromosomes that do not directly chromosomes that do not directly determine sex.determine sex.

In mammalsIn mammals

- 2 X chromosomes= FEMALE (XX)- 2 X chromosomes= FEMALE (XX)

- 1 X + 1 Y is a MALE (XY)- 1 X + 1 Y is a MALE (XY)

In mammals, males In mammals, males determine the sex of determine the sex of the offspringthe offspring

-each sperm has an equal chance of -each sperm has an equal chance of having an X or a Yhaving an X or a Y--however- the only option for eggs is to however- the only option for eggs is to receive an X chromosome.receive an X chromosome.1:1 male to female ratio1:1 male to female ratio

KaryotypesKaryotypes

Karyotype with an extra Karyotype with an extra chromosomechromosome

Linked & Linked & Sex-Linked GenesSex-Linked Genes

A. Linked genesA. Linked genes

Genes which are close Genes which are close together on same together on same chromosome.chromosome.

Inherited togetherInherited together Linked genes do not exhibit Linked genes do not exhibit

Mendel’s law of independent Mendel’s law of independent assortmentassortment

Chromosome MappingChromosome Mapping

The farther apart two genes are located The farther apart two genes are located on a chromosome, the on a chromosome, the more likely more likely a a cross-over will occur.cross-over will occur.

Researchers use recombinant Researchers use recombinant percentages to construct percentages to construct chromosome chromosome mapsmaps showing relative gene positions showing relative gene positions..

Sex-Linked traitsSex-Linked traits

are traits that are coded for by are traits that are coded for by alleles on a sex chromosome.alleles on a sex chromosome.

Genes found on the X chromosome are X-Genes found on the X chromosome are X-linked geneslinked genes

Since the X chromosome is larger- there are Since the X chromosome is larger- there are more X-linked than Y- linked traits.more X-linked than Y- linked traits.

NOTE: Since males have only 1 X- a male who NOTE: Since males have only 1 X- a male who carries the recessive allele will show the X-linked carries the recessive allele will show the X-linked trait.trait.

Sex Linked Sex Linked TraitsTraits

MutationsMutationsMutation Mutation --a change a change in thein the nucleotide-base nucleotide-base

sequence of a gene or DNAsequence of a gene or DNA -- Germ cellGerm cell- occurs in gametes- occurs in gametes

- can affect offspring- can affect offspring- - Somatic CellSomatic Cell-occur in organism’s body cells-occur in organism’s body cells

- may affect the organism (ex-cancer)- may affect the organism (ex-cancer) - does NOT affect offspring- does NOT affect offspring

MutationsMutations- Lethal Mutations- Lethal Mutations-cause death, often -cause death, often

before birthbefore birth

- Beneficial Mutations- Beneficial Mutations- result in - result in phenotypes that are beneficial .phenotypes that are beneficial .

Types of Chromosome Types of Chromosome MutationsMutations

1. Deletion1. Deletion- loss of a piece of chromosome due to - loss of a piece of chromosome due to breakage.breakage.

2. Inversion2. Inversion – a chromosome piece breaks off, – a chromosome piece breaks off, flips around backwards & reattachesflips around backwards & reattaches

3. Translocation3. Translocation – a piece of chromosome – a piece of chromosome breaks off & attaches to a non-homologous breaks off & attaches to a non-homologous chromosomechromosome

4.4. Non-DisjunctionNon-Disjunction – a chromosomes fails to – a chromosomes fails to separate from its homologue during meiosis. separate from its homologue during meiosis.

On your white board, with On your white board, with your partner, explain why your partner, explain why your assigned answer is your assigned answer is either correct or incorrect.either correct or incorrect.

Your assigned answer is the letter on your whiteboard!

Types of Chromosome Types of Chromosome MutationsMutations

Types of Chromosome Types of Chromosome MutationsMutations

An example of a human An example of a human disorder with a deletion disorder with a deletion error:error:

Cri du chat syndromeCri du chat syndrome- - missing part of chromosome 5- missing part of chromosome 5- cry of infants is similar to that of a cry of infants is similar to that of a

meowing kitten, due to problems with meowing kitten, due to problems with the larynx and nervous system. the larynx and nervous system.

About 1/3 of children lose the cry by age About 1/3 of children lose the cry by age 2. 2.

Types of Types of nondisjunction:nondisjunction: Trisomy- an extra chromosomeTrisomy- an extra chromosome leads to an leads to an individual with an extra chromosome in every cell of individual with an extra chromosome in every cell of his/her body. his/her body. 

Monosomy- is a deficiency in number of Monosomy- is a deficiency in number of chromosomeschromosomes and is defined as only one copy of a and is defined as only one copy of a chromosome that is normally present in two copies.    When chromosome that is normally present in two copies.    When fertilized, the outcome is 45 chromosomes in total.  fertilized, the outcome is 45 chromosomes in total.  Monosomies are less likely to survive when compared to Monosomies are less likely to survive when compared to trisomies.trisomies.

What causes non-What causes non-disjunction?disjunction? cause of non-disjunction is cause of non-disjunction is

unknown.  unknown.    non-disjunction occurs non-disjunction occurs

more frequently in the more frequently in the eggs of women as they eggs of women as they get older.get older.

Non- Disjunction Disorders Non- Disjunction Disorders with an extra chromosomewith an extra chromosome(these folks have 47 instead (these folks have 47 instead of the normal 46 of the normal 46 chromosomes in people):chromosomes in people):

Down syndrome- extra 21Down syndrome- extra 21 Edward’s Syndrome- extra 18Edward’s Syndrome- extra 18 Patau syndrome – extra 13Patau syndrome – extra 13

Examples Non Examples Non disjunction:disjunction:

Extra #21= Down’s Extra #21= Down’s SyndromeSyndrome

Extra #18= Extra #18= (most don’t live (most don’t live beyond 1beyond 1stst 7 months) 7 months) This girl is now 6.)This girl is now 6.)

http://starbulletin.com/96/03/25/news/story2.htmlhttp://starbulletin.com/96/03/25/news/story2.html

Sex-chromosome abnormalities Sex-chromosome abnormalities may also be caused by non-may also be caused by non-disjunction.disjunction.

Klinefelters Syndrome- XXYKlinefelters Syndrome- XXY ( extra X) ( extra X) Turners SyndromeTurners Syndrome – only 1 X- missing a – only 1 X- missing a

second X (XO)second X (XO) Super males XYYSuper males XYY Any combination (Any combination (up toup to XXXXY) produces XXXXY) produces

maleness.maleness. Males with more than one X are usually Males with more than one X are usually underdeveloped and sterile. underdeveloped and sterile.

XXX and XO womenXXX and XO women are usually sterile are usually sterile

Gene MutationsGene Mutations

changes in one or more of the changes in one or more of the nucleotides in a gene.nucleotides in a gene.

Types of Gene MutationTypes of Gene Mutation1. Point Mutation-1. Point Mutation- the substitution, addition the substitution, addition or removal of a single nucleotide, occurs or removal of a single nucleotide, occurs within a single gene or segment of DNAwithin a single gene or segment of DNA

2. Substitiution2. Substitiution- one nucleotide replaces - one nucleotide replaces anotheranother

3. Frameshift Mutation-3. Frameshift Mutation- if some if some nucleotides are deleted- whole segment nucleotides are deleted- whole segment movesmoves

4. Insertion Mutation 4. Insertion Mutation – one or more – one or more nucleotides added- also causes a frameshiftnucleotides added- also causes a frameshift

Gene MutationsGene Mutations

Which type of gene mutation Which type of gene mutation do you think would cause the do you think would cause the most serious errors?most serious errors?

Point mutationPoint mutation SubstitutionSubstitution FrameshiftFrameshift

Example: Example: substitution errorsubstitution error

Just 1 Amino Acid is Just 1 Amino Acid is a a Substitution Substitution ERRORERROR in Sickle Cell in Sickle Cell HemoglobinHemoglobin

Causes Hb to be Causes Hb to be sickle shaped instead sickle shaped instead of round- can’t fit into of round- can’t fit into red blood cells & red blood cells & changes their shape changes their shape too.too.

On your white board, with On your white board, with your partner, explain why your partner, explain why your assigned answer is your assigned answer is either correct or incorrect.either correct or incorrect.

ObjectiveObjective

Check3210.4.3 Apply data to complete Check3210.4.3 Apply data to complete and interpret a genetic pedigree.and interpret a genetic pedigree.

SPI 3210.4.5 Apply pedigree data to SPI 3210.4.5 Apply pedigree data to interpret various modes of genetic interpret various modes of genetic inheritance.inheritance.

Inheritance of TraitsInheritance of Traits

Pedigree Pedigree -- a diagram that a diagram that

shows howshows how a trait is inherited over a trait is inherited over several generationsseveral generations

Creating the foldableCreating the foldable

Reading a pedigreeReading a pedigree males are represented by squares males are represented by squares females by circlesfemales by circles. .

An individual who An individual who exhibits the traitexhibits the trait , , (for example, someone who suffers from Marfan (for example, someone who suffers from Marfan

syndrome), is represented by a syndrome), is represented by a filled symbolfilled symbol. .

A A horizontal linehorizontal line between two symbols is between two symbols is a a matingmating

HE

SHE

DAD MOM

Reading a PedigreeReading a Pedigree

The offspringThe offspring:: are connected to each other by a are connected to each other by a

horizontal linehorizontal line above the symbols above the symbols and to the parents by and to the parents by vertical lines.vertical lines.

Example pedigree:Example pedigree:

Is the mom or dad in generation I affected by a trait?Is the mom or dad in generation I affected by a trait? How many offspring are shown in generation II?How many offspring are shown in generation II? How many daughters & sons in generation II?How many daughters & sons in generation II? How many have the trait?How many have the trait? How many offspring does daughter #1 have? How How many offspring does daughter #1 have? How

many have the trait?many have the trait?

Dominant traitsDominant traits areare passed on passed on to a son or daughter EVEN to a son or daughter EVEN

if only if only one parentone parent has it. has it. Every affected individual has at least one Every affected individual has at least one

affected parent affected parent Affected individuals who mate with Affected individuals who mate with

unaffected individuals have a 50% chance unaffected individuals have a 50% chance of transmitting trait to each childof transmitting trait to each child

Two affected Two affected

parents may have parents may have

unaffected children.unaffected children.

Where did the trait seen in generation III come Where did the trait seen in generation III come from?from?

Traits can be passed on to children if Traits can be passed on to children if both both parentsparents, even if they may seem "normal”, , even if they may seem "normal”, are are carrierscarriers of the recessive trait. of the recessive trait.

Recessive Pedigree

Recessive pedigree:Recessive pedigree:

If individuals 2 + 3 in generation 3 have more children- will they be affected?Can Individual #8 in gen. 3 have any unaffected children?Can individual #9 in gen 3 have affected children?

Example pedigree of Example pedigree of cystic fibrosis cystic fibrosis

www.cfscreening.com.au/.../CF/CFInherited.shtml

ObjectiveObjective

3210.4.4 Compare different modes of 3210.4.4 Compare different modes of inheritance: sex linkage, co-dominance, inheritance: sex linkage, co-dominance, incomplete dominance, multiple alleles and incomplete dominance, multiple alleles and polygenic traitspolygenic traits

3210.1.6 Describe the connection between 3210.1.6 Describe the connection between mutations and human genetic disordersmutations and human genetic disorders

3210.4.7 Assess the scientific and ethical 3210.4.7 Assess the scientific and ethical ramifications of emerging genetic technologiesramifications of emerging genetic technologies

Polygenic InheritancePolygenic Inheritance

- traits influenced by several genes - traits influenced by several genes

(most human characteristics)(most human characteristics)

example- example- skin colorskin color is additive effect of is additive effect of 6 genes6 genes

Complex CharactersComplex Characters

traits influenced by both genes & traits influenced by both genes & environment environment

Example- Example- heightheight

3. Multiple Alleles3. Multiple Alleles--

genes with genes with 3 or more alleles3 or more alleles. .

Example- human blood typeExample- human blood type. . IAIA, , IBIB, , ii 3 alleles- both IA & IB are dominate over i, 3 alleles- both IA & IB are dominate over i,

Codes for sugars that are on blood cell Codes for sugars that are on blood cell surfacesurface. .

four different blood types- four different blood types- AA, , BB, , AABB, , OO

What are the 2 genotypes for “type B?What are the 2 genotypes for “type B? Which blood type can donate to all the others? Which blood type can donate to all the others?

(universal donor?)(universal donor?) Which blood type makes antibodies (will clot Which blood type makes antibodies (will clot

against) both A & B blood types?against) both A & B blood types?

Incomplete DominanceIncomplete Dominance

there is an there is an intermediate phenotypeintermediate phenotype Human example- Human example- wavy hair wavy hair is the is the

intermediate between straight & curly hairintermediate between straight & curly hair

(remember chapter 9 plant example:(remember chapter 9 plant example: - pink 4 o’clock flowers,- pink 4 o’clock flowers,

In between red & white flowers)In between red & white flowers)

X-linked TraitsX-linked Traits

Traits that are on the X chromosome. Traits that are on the X chromosome.

Since males only have one X Since males only have one X chromosome- they are affected more chromosome- they are affected more than femalesthan females

Females have 2 chances to get a Females have 2 chances to get a good copy of the gene but males good copy of the gene but males only get 1 chance. only get 1 chance.

Examples of human X-Examples of human X-linked traitslinked traits Hemophilia- Hemophilia- blood clotting disorder- blood clotting disorder-

boys may bleed to deathboys may bleed to death Duchene muscular dystrophy -Duchene muscular dystrophy -affects affects

cardiac and skeletal muscle, as well as cardiac and skeletal muscle, as well as some mental functions. some mental functions.

Fragile-X syndrome- Fragile-X syndrome- part of X part of X chromosome has errors- most common chromosome has errors- most common cause of mental retardation in malescause of mental retardation in males

Red-green color blindness- Red-green color blindness- males males cannot see these 2 colors.cannot see these 2 colors.

Sex- Influenced TraitsSex- Influenced Traits

males & females show different males & females show different phenotypes with same genotype- phenotypes with same genotype-

example- example- male pattern baldnessmale pattern baldness

7. Single Allele Traits7. Single Allele Traits

trait controlled by 1 allele- Dominant or trait controlled by 1 allele- Dominant or RecessiveRecessive

Dominant Examples: Dominant Examples: Achondroplastic dwarfismAchondroplastic dwarfism-- dwarf size dwarf size

PolydactlyPolydactly is the presence of a sixth digit. is the presence of a sixth digit.

Huntington's diseaseHuntington's disease (also called Woody (also called Woody Guthrie's disease)-progressive destruction of Guthrie's disease)-progressive destruction of brain cells after age 30brain cells after age 30

Marfans Syndrome- Marfans Syndrome- progressive connective progressive connective tissue disorder. (some cases are new mutations tissue disorder. (some cases are new mutations with no family history)with no family history)

Single allele recessive Single allele recessive traits:traits:

AlbinismAlbinism lack of pigmentation in skin, hair, and lack of pigmentation in skin, hair, and eyes, -Homozygous recessive (aa) people make eyes, -Homozygous recessive (aa) people make no pigmentsno pigments

PKU (Phenylketonuria)PKU (Phenylketonuria) - lack enzyme to use the - lack enzyme to use the amino acid phenylalanine, buildups breakdown amino acid phenylalanine, buildups breakdown products leads to mental retardation. 1 in 15,000 products leads to mental retardation. 1 in 15,000 infants has- treat with infants has- treat with DIET! (no DIET! (no phenylalanine)phenylalanine)

Tay-Sachs Disease-Tay-Sachs Disease- degeneration of the nervous degeneration of the nervous system. Children rarely survive past five years of system. Children rarely survive past five years of age. age.

Maple Syrup Urine Disease (MSUD)Maple Syrup Urine Disease (MSUD) –like PKU –like PKU amino acids leucine, isoleucine, and valine amino acids leucine, isoleucine, and valine

More single allele recessive More single allele recessive examples:examples: Sickel Cell AnemiaSickel Cell Anemia- single amino acid - single amino acid

substitution in hemoglobin causes lack substitution in hemoglobin causes lack of oxygen to bodyof oxygen to body

Cystic fibrosis-Cystic fibrosis- body creates sticky body creates sticky thick mucus – chloride ions- detected in thick mucus – chloride ions- detected in SWEAT TEST.SWEAT TEST. - was once considered a - was once considered a fatal childhood disease- modern fatal childhood disease- modern treatments can increase lifespan to 30 treatments can increase lifespan to 30 years plus.years plus.

Detecting Genetic Detecting Genetic DiseaseDisease

1. 1. TestingTesting Amniocetesis- Amniocetesis- Dr removes some amniotic fluid, Dr removes some amniotic fluid,

14th-18th week of pregnancy, analyze fluid for 14th-18th week of pregnancy, analyze fluid for proteins & look at chromosomes- some risk of proteins & look at chromosomes- some risk of pregnancy losspregnancy loss

Chorionic Villi Sampling-Chorionic Villi Sampling- clip cells from clip cells from placental area- 8-14th week pregnancyplacental area- 8-14th week pregnancy

2. Treatments-2. Treatments- vary with disease vary with disease