Human Inheritance Disorders caused by individual genes dominant Individuals with the disorder only need 1 allele to have the disorder Huntingtons Disease Caused by a repeat of the sequence CAG ID: 784652
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Slide1
Chapter 12
Chromosomes and
Human Inheritance
Slide2Disorders caused by individual genes - dominant
Individuals with the disorder only need 1 allele to have the disorder
Huntington’s Disease
Caused by a repeat of the sequence CAG Mental retardation and uncontrollable movements that usually don’t appear until middle ageAchondroplasia (mom and son)A form of dwarfism Polydactyly6 fingers or toes
Slide3Disorders caused by individual genes – some say recessive – really
codominant
To have the disorder you need 2 copies of the gene
Sickle cell disease Defect in hemoglobin (oxygen carrying molecule in red blood cells) causes red blood cells to “sickle”Carried by 1/12 African AmericansCarriers are healthy but are highly resistant to malaria.
Slide412.1 Human Chromosomes
In humans, two
sex chromosomes
are the basis of sex – human males have XY sex chromosomes, females have XXAll other human chromosomes are autosomes – chromosomes that are the same in males and females
Slide5Sex Determination in Humans
Sex of a child is determined by the father
Eggs have an X chromosome; sperm have X or Y
Slide6Sex Determination in Humans
The
SRY gene on the Y chromosome is the master gene for male sex determination
Triggers formation of testes, which produce the male sex hormone (testosterone)Without testosterone, ovaries develop and produce female sex hormones (estrogens)What makes a boy a boy and a girl a girl? It’s not that simple……….SRY gene
Slide7Karyotyping
Karyotype
A micrograph of all metaphase chromosomes in a cell, arranged in pairs by size, shape, and length
Detects abnormal chromosome numbers and some structural abnormalitiesConstruction of a karyotypeColchicine stops dividing cells at metaphaseChromosomes are separated, stained, photographed, and digitally rearranged
Slide8Fig. 12-3a, p. 187
Slide9Fig. 12-3b, p. 187
Slide10Down Syndrome
Trisomy
21
Slide11Turner Syndrome
1/ 2,000 live female births
Short stature, loss of ovarian function, lack or incomplete development at puberty
Heart defect, infertility, webbed neck
Slide12Klinefelter’s
Syndrome
1/500-1/1000 males
Small testes and less testosterone than normal (less facial hair, infertility, breast development)Tall
Slide13Nondisjunction
Chromosomes don’t separate in
meiosis
Slide14Chromosomal Mutations
Deletion
– involves the loss of part of a chromosome
Duplication – involves an extra copy of part or all of the chromosomeInversion – reverses the direction of part of the chromosomeTranslocation – when part of one chromosome breaks off and attaches to another
Slide15Changes in Chromosome Structure
Cri-du-chat – “Cat’s cry”
Deletion in Chromosome 5
Mental impairment, abnormally shaped larynx that causes infants to make distinct cat-like meow , low set ears
Slide16Disorders caused by individual genes – sex-linked
Genes in sex-linked disorders are found on the X or Y chromosome (most are on X)
Color blindness (X chromosome)
Humans have 3 genes for color vision – all on the XRed-green colorblindness = 1/12 males & 1/200 femalesMales have 1 X chromosomes – females have 2 (the allele for colorblindness can be masked in females)
Slide17Colorblindness
Slide18Hemophilia – Remember the Romanovs?
X-linked recessive
interferes with blood clotting – bruise easily, internal bleeding causes joint problems
Slide19Duchenne
Muscular Dystrophy (DMD)
1/3500 people – x-linked recessive
Causes abnormal dystrophin (a protein that supports muscle fibers) that causes muscle cells to dieProgressive disorder – usually diagnosed between 3 and 7, wheelchair by 12 and early death from heart or respiratory failure.
Slide20Sex linked problems
1) A female is a carrier for hemophilia and the dad is normal
What percent of sons will have hemophilia?
What percent of daughters will have hemophilia?
Slide212
) Show how a daughter can be a carrier for colorblindness
from either her mom or dad.
Slide22Pedigree Analysis
Slide23How is this trait inherited?
Slide24How is this trait inherited?
What is the genotype of individual III 1? I 2?
Slide25How is this trait inherited?
Slide26Slide27Well…..it’s not that simple……
Epigenetics
– “above the genome”
Factors that control gene expression that do not change the DNA or RNANova – Ghost in Your Genes!!!!