chromosomal inheritance chromosomal division for sperm and egg production chromosomal abnormalities
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Chromosomal InheritanceChromosomal Inheritance
Chromosomal Division for Chromosomal Division for Sperm and Egg ProductionSperm and Egg Production
Chromosomal AbnormalitiesChromosomal Abnormalities
Human Life CycleHuman Life Cycle
Nuclear division reducing the chromosome
number, leading to sperm or eggs
Diploid number of chromosomes,
two full sets
Haploid number of chromosomes,
one full set
Nuclear division retaining the original chromosome number
Cell Cycle With Meiosis Cell Cycle With Meiosis
G1cytoplasm doubles, including organelles
Schromosomesduplicate
G2synthesis of proteins and assembly of components for division
cytokinesis
Meiosis Interphase includes Interphase includes
G1 = growth phase 1G1 = growth phase 1 S = synthesis phaseS = synthesis phaseG2 = growth phase 2G2 = growth phase 2
Interphase
Meiosis IIcytok
inesis
Meios
is I
Meiosis includes two Meiosis includes two chromosomal divisionschromosomal divisions
Meiosis IMeiosis IMeiosis IIMeiosis II
Cytokinesis = division ofCytokinesis = division of cytoplasmic contents cytoplasmic contents
Homologous Chromosome PairsHomologous Chromosome Pairs
• Diploid cells have Diploid cells have pairs of pairs of chromosomeschromosomes
• Each homologous Each homologous chromosome pair is chromosome pair is genetically matched genetically matched so that the genes are so that the genes are arranged in the arranged in the same order same order
• Meiosis distributes Meiosis distributes members of each members of each pair to separate pair to separate nucleinuclei
Humans have 1 pair of sex chromosomes and 22 pairs of autosomes
Outcome of Meiotic DivisionsOutcome of Meiotic DivisionsDiploid Human Cell with 46 chromosomes (23 pairs)Diploid Human Cell with 46 chromosomes (23 pairs)
Duplication of Cell ContentsDuplication of Cell Contents
Meiosis I: Reduction DivisionMeiosis I: Reduction DivisionSeparation of Homologous Separation of Homologous Chromosomes into Different NucleiChromosomes into Different Nuclei
2 Genetically-Different Haploid Human Cells with 23 2 Genetically-Different Haploid Human Cells with 23 duplicated chromosomesduplicated chromosomes
Meiosis II: Equational DivisionMeiosis II: Equational DivisionSeparation of Duplicated Chromosomes Separation of Duplicated Chromosomes into Different Nucleiinto Different Nuclei
4 Genetically-Different Haploid Human Cells with 23 4 Genetically-Different Haploid Human Cells with 23 chromosomeschromosomes
Duplicated Duplicated ChromosomesChromosomes
in Early Meiosis in Early Meiosis
Homologous Homologous Chromosome Pair Chromosome Pair
Association of four chromatids of a
duplicated homologous
chromosome pair
Centromere = constricted region
Duplicated chromosomes joined at their centromeres
Nonsister Chromatids are joined to differentcentromeres
Prophase I of Meiosis IProphase I of Meiosis I
Chromosomes thickenChromosomes thickenGenetic exchange occurs between nonsister Genetic exchange occurs between nonsister chromatids through crossing-over chromatids through crossing-over
Metaphase I of Meiosis IMetaphase I of Meiosis I
Homologous pairs line up at the cell equatorHomologous pairs line up at the cell equatorSpindle fibers attached to centromeres cause Spindle fibers attached to centromeres cause chromosomal movement chromosomal movement
Spindle fiber
Anaphase I and Telophase I Anaphase I and Telophase I
of Meiosis Iof Meiosis I
Anaphase IAnaphase IMembers of homologous pair Members of homologous pair separate and are pulled to separate and are pulled to opposite poles of the cell opposite poles of the cell
Telophase ITelophase IChromosomes reach oppositeChromosomes reach opposite poles poles
+ cytokinesis
CytokinesisCytokinesisCytoplasm divides into two Cytoplasm divides into two separate cells separate cells
Daughter cells are haploid with duplicated chromosomes
Prophase II and Metaphase II Prophase II and Metaphase II of Meiosis IIof Meiosis II
Prophase IIProphase IIChromosomes thickenChromosomes thicken
Metaphase IIMetaphase IIChromosomes line up Chromosomes line up at cell equator at cell equator
Anaphase II and Telophase II Anaphase II and Telophase II of Meiosis IIof Meiosis II
Anaphase IIAnaphase IISister Chromatids Sister Chromatids separate and move to separate and move to opposite poles opposite poles
Telophase IITelophase IIChromosomes have Chromosomes have reached opposite poles reached opposite poles + cytokinesis
CytokinesisCytokinesisCytoplasm divides into Cytoplasm divides into
separate cells separate cells Daughter cells are haploid
and have genetic differences
Sperm formationSperm formation•Equal divisions of cytoplasmEqual divisions of cytoplasm•Four functional products per meiosisFour functional products per meiosis
Egg formationEgg formation•Unequal divisions of cytoplasmUnequal divisions of cytoplasm•Small polar bodies formedSmall polar bodies formed•One functional product per meiosisOne functional product per meiosis
Fertilization occurs after Meiosis I and
stimulates Meiosis II
Sex DeterminationSex Determination Sex ChromosomesSex Chromosomes: homologous : homologous
chromosomes that differ in size and chromosomes that differ in size and genetic composition between males and genetic composition between males and femalesfemales
Human Human ChromosomeChromosome
XX YY
SizeSize LargerLarger SmallerSmallerGenetic Genetic CompositionComposition
Multiple Multiple genesgenesunrelated unrelated to genderto gender
Very few genesVery few genes
TDF region TDF region determines determines maleness maleness
Chromosomal Number AbnormalitiesChromosomal Number Abnormalities
Arise by Nondisjunction = Failure of homologous Arise by Nondisjunction = Failure of homologous chromosomes or chromatids to separate during chromosomes or chromatids to separate during meiosismeiosis
Nondisjunction during Meiosis IINondisjunction during Meiosis IINondisjunction during Meiosis INondisjunction during Meiosis I
Human Autosomal AbnormalityHuman Autosomal Abnormality
How can Down Syndrome occur? How can Down Syndrome occur?
Eg. Egg with 2 copies of #21 Eg. Egg with 2 copies of #21 (24 chromosomes)(24 chromosomes) + Sperm with 1 copy of #21 + Sperm with 1 copy of #21 (23 chromosomes)(23 chromosomes) = Embryo with 3 copies of #21 = Embryo with 3 copies of #21 (47 chromosomes)(47 chromosomes)
Down SyndromeDown Syndrome Trisomy 21Trisomy 21
Three copies of Three copies of chromosome 21chromosome 21
Karyotype for Down SyndromeKaryotype for Down Syndrome
Eye foldEye fold Palm CreasePalm Crease
Physical FeaturesPhysical Features
Human Sex Chromosome AbnormalityHuman Sex Chromosome Abnormality Turner SyndromeTurner Syndrome XOXO
One copy of XOne copy of XNo second sex No second sex chromosomechromosome
How can Turner Syndrome occur?How can Turner Syndrome occur?Eg. Egg with 0 copies of XEg. Egg with 0 copies of X (22 chromosomes) (22 chromosomes) +Sperm with 1 copy of X+Sperm with 1 copy of X (23 chromosomes) (23 chromosomes) = Embryo with 1 copy of X= Embryo with 1 copy of X (45 chromosomes) (45 chromosomes)
Non-functional Ovaries From Adult Non-functional Ovaries From Adult Female with Turner’s SyndromeFemale with Turner’s Syndrome
Normal uterus, tubesNormal uterus, tubes and ovariesand ovaries
Karyotype for Karyotype for Turner’s SyndromeTurner’s Syndrome
Other Human Sex Chromosome Other Human Sex Chromosome Number AbnormalitiesNumber Abnormalities
Klinefelter Klinefelter SyndromeSyndrome
XXYXXY
Poly-X Poly-X FemalesFemales
XXXXXX
Jacobs Jacobs SyndromeSyndrome
XYYXYY
Sterile MaleSterile Male
Fertile FemaleFertile Female
Fertile MaleFertile Male
Chromosome Structure AbnormalitiesChromosome Structure Abnormalities
Williams syndrome is caused by a Williams syndrome is caused by a deletiondeletion = loss of a chromosomal segment. = loss of a chromosomal segment.
Chromosome Structure AbnormalitiesChromosome Structure Abnormalities
Alagille syndrome is caused by a Alagille syndrome is caused by a translocationtranslocation = = movement of a chromosomal segment to another movement of a chromosomal segment to another non-homologous chromosome.non-homologous chromosome.
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