Download Chromosomes and Human Inheritance

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Complement component 4 wikipedia, lookup

Chromosomes and
Human Inheritance
Disorders 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 age
Achondroplasia (mom and son)
A form of dwarfism
6 fingers or toes
Disorders 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 Americans
 Carriers are healthy but are highly resistant
to malaria.
12.1 Human Chromosomes
 In humans, two sex chromosomes are the basis of
sex – human males have XY sex chromosomes,
females have XX
 All other human chromosomes are autosomes –
chromosomes that are the same in males and
Sex Determination in Humans
 Sex of a child is determined by the father
 Eggs have an X chromosome; sperm have X or Y
Sex 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
SRY gene
 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
 Construction of a karyotype
 Colchicine stops dividing cells at metaphase
 Chromosomes are separated, stained, photographed, and
digitally rearranged
Fig. 12-3a, p. 187
Fig. 12-3b, p. 187
Down Syndrome
 Trisomy 21
Turner Syndrome
 1/ 2,000 live female births
 Short stature, loss of ovarian function, lack or
incomplete development at puberty
 Heart defect, infertility, webbed neck
Klinefelter’s Syndrome
 1/500-1/1000 males
 Small testes and less testosterone than normal (less
facial hair, infertility, breast development)
 Tall
 Chromosomes don’t separate in
Chromosomal Mutations
 Deletion – involves the loss of part of a chromosome
 Duplication – involves an extra copy of part or all of
the chromosome
 Inversion – reverses the direction of part of the
 Translocation – when part of one chromosome breaks
off and attaches to another
Changes 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
Disorders 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 X
 Red-green colorblindness = 1/12 males &
1/200 females
 Males have 1 X chromosomes – females
have 2 (the allele for colorblindness can be
masked in females)
Hemophilia – Remember the Romanovs?
 X-linked recessive
 interferes with blood clotting – bruise easily, internal
bleeding causes joint problems
Duchenne Muscular Dystrophy (DMD)
 1/3500 people – x-linked recessive
 Causes abnormal dystrophin (a protein that supports
muscle fibers) that causes muscle cells to die
 Progressive disorder – usually diagnosed between 3
and 7, wheelchair by 12 and early death from heart or
respiratory failure.
Sex linked problems
 1) A female is a carrier for hemophilia and the dad is
What percent of sons will have hemophilia?
What percent of daughters will have hemophilia?
2) Show how a daughter can be a carrier for colorblindness from
either her mom or dad.
Pedigree Analysis
How is this trait inherited?
How is this trait inherited?
What is the genotype of individual III 1? I 2?
How is this trait inherited?
Well…’s not that simple……
 Epigenetics – “above the genome”
 Factors that control gene expression that do not change the
 Nova – Ghost in Your Genes!!!!