Have you taken the latest quiz When is your next paper due If you are not sure you need to Discover Biology FIFTH EDITION CHAPTER 13 Chromosomes and Human Genetics 2012 W W Norton amp Company Inc ID: 467184
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Log into PAL
Have you taken the latest quiz?
When is your next paper due?
If you are not sure, you need toSlide2
Discover Biology
FIFTH EDITION
CHAPTER
13Chromosomes and HumanGenetics
© 2012 W. W. Norton & Company, Inc.
Anu Singh-Cundy • Michael L. CainSlide3
Genes & ChromosomesChromosome: one LONG DNA molecule
Wrapped around histone proteins
Many genes on each chromosomeSlide4
Genes & Chromosomes23 pairs of
chromosomes
~25,000 genesSlide5
VocabularyLoc
us –
location of a gene on a chromosome
Autosomes – chromosomes that don’t control sex 44 of our 46 chromosomes are autosomesSex chromosomes – they control our sex 2 of our 46 one X, one that is either X or Y XX=female, XY=male
Slide6
Genes on sex chromosomesGenes on X chromosome
women have 2 copies, men have 1Genes on Y chromosome men have 1 copy, women have noneMen don’t like recessive disorders on sex chromosomes!!!Slide7
SRY: The maleness geneOne gene on Y controls all other genes that cause male traits
No SRY?
Develop as a femaleSlide8
Mendel was WRONG!!Mendel’s “law of independent assortment”
only
if genes are on different chromosomesSome genes are normally inherited together “genetically linked” stuff on the same chromosomeSlide9
Crossing-Over VS Genetic LinkageGenes on same chromosome (
linked
)
normally inherited together crossing over can alter A & C: linkedB & C: tightly linked (less likely to separate via crossover)Slide10
Genetic Linkages cause weird ratios
Genes on same chromosome
often
move together
Mendel got lucky: all 7 traits on different chromosomes
Weird ratios
No independent assortmentSlide11
Pedigree: Who’s your daddy?pedigree: a chart showing genetic relationships
for two or more generations
Geneticists use to study inheritance Slide12
Example: Pedigree ChartPedigree chart for X-linked recessive
heterozygoteSlide13
Genetic DisordersSomatic mutations: not passed on to kids
Mutations in gametes:
can be passed on
Sources of genetic disorders:Mutations in individual genesAbnormal chromosome number Gene turned on/off (epigenetics) not in book!!!Slide14Slide15
Single-Gene MutationsMany are recessive
Can have dominant gene and phenotype
look/act normal but carry disease can skip generations Slide16
Autosomal Recessive Disorders3:1 = 75% chance of no symptoms
recessives more likely to stay
in population
heterozygotes can pass on without symptoms e.g. lethal recessives passed onSlide17
Autosomal Dominant Disorders
Affect
more of offspring
50% chance of passing on to the children
More rare
If
you can’t breed, won’t pass
on
Removed via natural selection
Tend to be new mutations
Exception:
Huntington’s
why? Symptoms show up later in lifeSlide18
Huntington’s Diseasecaused by dominant allele
50% chance child has
Coordination, cognitive decline
Nursing home in middle ageOld Days: give to kids before you know you haveNow: numbers down, genetic testing & councilingSlide19
Sex linked Mutationson the X or Y chromosome
There are about 50 human
Y-linked
genes and approximately 1,100 human X-linked genesSlide20
Sex-Linked disordersLess common in women (XX)
X linked: 2 copies of recessive before she’s affected
Y linked: immuneSlide21
Genes on sex chromosomesGenes on X chromosome
women have 2 copies, men have 1Genes on Y chromosome men have 1 copy, women have noneMen don’t like recessive disorders on sex chromosomes!!!Slide22
Sex-Linked disordersMore common in men X: dominant or recessive, he has it
Y: dominant or recessive he has it
No other copy of chromosome to blockSlide23
Genetic variationCrossing-over
Independent assortment of chromosomes
FertilizationSlide24
Junction: where things come together
Disjunction: where things separate
Non-disjunction
: mistake in separating chromatids during meiosisSlide25
Nerd WordsAneuploidy = has an unusual number of chromosomes
Monosomy
= has one copy of a chromosomeTrisomy = has three copies of a chromosome
Down’s Syndrome is caused by trisomy 21Slide26
Syndromes from AneuploidyDown’s Syndrome = trisomy 21
Edward’s Syndrome = trisomy 18
Kleinfelter’s Syndrome = XXY
Turner’s Syndrome = XOXYY SyndromeSlide27
Ways to alter chromosomes
Misalignment/ separation errors
Can cause insertions, deletions, duplications, translocations, inversions, etc
.Pay attention: at least one picture will be on testSlide28
Ways to alter chromosomesMistakes in prophase move sections of chromosomesSlide29
Ways to alter chromosomesSlide30
Duplication: an important role in evolution two copies: one has original function one mutates to new function
Ways to alter chromosomesSlide31
Mutation: cause & effectCan cause mutations:
Mistakes in DNA replication
Collisions of the DNA molecule with other molecules
Damage from heat or chemical agentsEffect: Only mutations in gametes matter if you can’t inherit it, it won’t have an effect on the population (must pass on to cause evolution)Slide32
Clicker Questions
CHAPTER 13
Chromosomes and Human
GeneticsSlide33
Concept QuizWhich of the following is
not
true of homologous chromosomes?
They contain the same alleles.They contain the same genes.One came from each parent.Each is duplicated during replication.Slide34
Genes that are linked on the same chromosome always segregate together.
True
False
Concept QuizSlide35
Concept QuizAutosomal‑dominant disorders
Are carried on the X chromosome.
Often express late in life.
Are spread by carriers (heterozygotes) mating.Are more common than recessive disorders.Slide36
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