11.1 basic patterns of human inheritance
DESCRIPTION
11.1 BASIC PATTERNS OF HUMAN INHERITANCE. WHAT YOU WILL LEARN -How to determine if an inherited trait is dom/rec -Examples of DOMINANT/RECESSIVE disorders -Construct / Interpret PEDIGREES. READING Q ’ s. 1-IDENTIFY - PowerPoint PPT PresentationTRANSCRIPT
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11.1 BASIC PATTERNS OF HUMAN INHERITANCE
WHAT YOU WILL LEARN-How to determine if an inherited trait is dom/rec-Examples of DOMINANT/RECESSIVE disorders-Construct / Interpret PEDIGREES
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READING Q’s
1-IDENTIFY-Check the term that describes the genotype of a person who expresses a recessive trait
-HOMOZYGOUS: organism with 2 of the same alleles for a particlular trait-aa
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READING Q’s
2-CATEGORIZE: The following genetic disorders as RECESSIVE or DOMINANT
a-albinism recessivedominant
b-Huntington's recessive dominantc-cystic fibrosisrecessive dominant
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READING Q’s
3-EXPLAIN-For what purpose is a genetic pedigree used?
-study genetic relationships-trace inheritance of a trait generation to generation
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READING Q’s
4-DRAWThe symbols that are used to represent a male AND female in a pedigree
MALE- FEMALE-
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READING Q’s
5-EVALUATE-Circle the carriers in the second generation
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READING Q’s
6-CALCULATE-What percentage of the children in this family inherited Tay-Sachs disease?
-1/4=25%
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READING Q’s
7-IDENTIFY-Do any grandchildren in this family have polydactyly?
-NO
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READING Q’s
8-EXPLAIN-Why are recessive traits difficult to study?
-Not all people who carry the recessive allele have the trait
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GROUP WORK: APPLICATION NOTES
-As a group complete the areas below using your knowledge from the reading/discussion.MAIN IDEAREVIEW VOCABRECESSIVE / DOMINANT GENETIC DISORDERS
VOCAB-carrier-pedigree
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MAIN IDEA
-PEDIGREESinheritance of traits over several generations
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REVIEW VOCAB
DEFINE: gene-segment of DNA on chromosome
DEFINE: homozygous-2 identical alleles [TT / tt]
DEFINE: heterozygous-2 different alleles [Tt]
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RECESSIVE/DOMINANT GENETIC DISORDERS
COMPARE/CONTRAST:recessive and dominant genetic disorders
RECESSIVE-expressed when indv HOMO recessive [tt]
DOMINANT-expressed when indv HOMO dominant [TT] or HETERO [Tt]
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RECESSIVE/DOMINANT GENETIC DISORDERS
EXPLAIN why recessive disorders are more common than dominant disorders.
-DOMINANT: only one allele must be inherited to be affected
-if DOM trait interferes w/ survival- no pass on
-RECESSIVE: carriers do NOT display the disorder-many carriers are unaware they carry an
affected gene
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RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY: the disease for each dominant/recessive disorders-caused by altered genes; results in lack of skin pigmentation
-ALBINISM-RECESSIVE
-characterized by body’s inability to tolerate galactose-GALATOSEMIA-RECESSIVE
-gene found on chromosome 15;characterized by lack of enzyme that breaks down fatty acids
-TAY SACHS-RECESSIVE
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RECESSIVE/DOMINANT GENETIC DISORDERS
IDENTIFY: the disease for each dominant/recessive disorders-affects the nervous system; no treatment; breaks down part of brain
-HUNINGTON’S-DOMINANT
-affects mucus-producing glands, digestive enzymes, sweat glands
-CYCTIC FIBROSIS-RECESSIVE
-affects height and body size-ACHONDROPLASIA-DOMINANT
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RECESSIVE/DOMINANT GENETIC DISORDERS
PREDICT: what are the chances of 2 carriers of cystic fibrosis having a child with cystic fibrosis?
¼= 25% F f
F f
FF Ff
Ff ff
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RECESSIVE/DOMINANT GENETIC DISORDERS
Positive Exposure
Positive exposure video clip Rick Guidotti - PART 2
Positive Exposure Inside Edition Part I - YouTube
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PEDIGREE BASICS[the FAMILY TREE of genetics]WHAT is it:-diagram explaining genetic history
WHO uses it:-scientist-genetic counselors
WHY use it:-probability of child having disorder/condition-determine disorder/condition as autosomal/sex linked
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PEDIGREES
SUMMARIZE: pedigree symbolsMALE
-sqaure-FEMALE
-circle-AFFECTED MALE
-shaded square-AFFECTED FEMALE
-shaded circle-
CARRIER-half shaded symbol- / PARENTS/OFFSPRING-line down from parent, circles/squares on second row
PARENTS-circle joined to square-GENERATIONS-I, II , III, IV, V
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STEPS for INTERPRETING PEDIGREES1- DETERMINE if the pedigree chart is showing: AUTOSOMAL or X-LINKED disorder
-autosomal:-If it is a 50/50 ratio between men and women
-x-linked:-If most of the males in the pedigree are affected
2- DETERMINE if disorder is DOMINANT or RECESSIVE-dominant:
-one of the parents must have the disorder.-recessive
-neither parent has to have the disorder because they can be heterozygous.
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Connecting Pedigree Symbols
Married Couple
Siblings
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EX- PEDIGREE CHART
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PRACTICE INTERPRETING
1. Determine if the pedigree chart shows an autosomal or X-linked disease.
-If most of the males in the pedigree are affected the disorder is X-linked
-If it is a 50/50 ratio between men and women the disorder is autosomal.
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PRACTICE: Interpreting
Is it Autosomal or X-linked?
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Answer
Autosomal
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Interpreting a Pedigree Chart2. Determine whether the disorder is
dominant or recessive
-If the disorder is dominant, one of the parents must have the disorder.
-If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.
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Dominant or Recessive?
PRACTICE: Interpreting
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Answer
Dominant
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• Dominant or Recessive?
PRACTICE: Interpreting
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Answer
• Recessive
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ANALYZING PEDIGREES
EVALUATE: the inheritance of achondroplasia shown in the pedigree
-parent w/ disorder-father
-#children with disorder-1 / 1st born son
-genotype of younger son-homozygous recessive / aa
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ANALYZING PEDIGREESANALYZE and RESPOND:
-RECALL if the trait is rec or dom based on the following information: -individuals I-1 and I-2 are unaffected but have affected childRECESSIVE DOMINANT-SPECIFIY if parents II-1 and II-2, who have an affected child, are carriers of that traitCARRIER NOT A CARRIER-TELL whether there is a dominant gene in the genotype of II-4NONE A LEAST ONE-Individual II-1is in generation 2 TRUE FALSE
X
X
X
X
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ANALYZING PEDIGREES
THINK BACK and RESPOND: -A scientist uses a pedigree to study family historyTRUE FALSE-A pedigree traces the inheritance of a particular trait through only two generationsTRUE FALSE-In a pedigree, one who does not express the trait is represented by a darkened circle/squareTRUE FALSE-In a pedigree, a horizontal like between 2 symbols shows that these individuals are the parents of the offspringTRUE FALSE
X
X
X
X
MANY
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ANALYZING PEDIGREES
DIAGRAM: Suppose both parents can roll their tongues but their son cannot.[TONGUE ROLLING = DOMINANT / T]DRAW a pedigree showing this trait LABEL each symbol with the appropriate genotype
What was the probability that they would have a non-tongue roller offspring? (hint: punnet square)
-both parents carry recessive gene-parent genotype Tt-son genotype tt
-probability of child tt= 25%
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PEDIGREE CHART PRACTICE
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PEDIGREE PRACTICE A
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PEDIGREE PRACTICE B
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PEDIGREE PRACTICE C
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PEDIGREE PRACTICE D
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INVESTIGATING HUMAN PEDIGREES
-USE the information provided in the transcript to construct a pedigree showing hairy earlobes* in a family *HE
-DETERMINE the oldest couple in the family-DRAW their pedigree symbols—include names-CONTINUE with other members in the family-DETERMINE genotypes as you gather enough information