Week 13 - meiosis inheritance connection

Question 1

Sex linkage

Answer 1

Genes on X chromosome are called X-linked

• males only have one X chromosome, so one copy of a recessive allele will result in recessive phenotype in men
• women have two copies of X so can be heterozygous of X-linked recessive trait w/o showing phenotype
  eg: hemophilia, colour blindness, muscular dystrophy

Question 2

Red-green colour blindness

Answer 2

• colour blindness is an X-linked recessive disorder.

- the inability to differentiate certain colour perceptions

Question 3

hemophilia

Answer 3

• disease that affects single protein in a cascade of proteins involved in formation of blood clots
• form of hemophilia cased by x-linkedrecessive allele → heterozygous females are asymptomatic carriers

Question 4

dosage compensation

Answer 4

• in each female cell
• all but one X-chromosome is inactivated and is highly condensed into a Barr body
• ENSURES AN EQUAL’ expression of genes from the sex chromosomes even though females have two X chromosomes and males have one
• females heterozygous for genes on the X chromosome are genetic mosaics

Question 5

nondisjunction of sex chromosomes

Answer 5

• do not generally experience severe developmental abnormalities
• individuals have somewhat abnormal features but often reach maturity in some cases may be fertile
• XXX : female
• XXY: male → klinefelter syndrome
• XO: female →turner syndrome
• OY: nonviable zygoes
• XYY: makles → jacob syndrome
• if dosage compensation occurs in females, why do XO females or XXY males show a phenotype

Question 6

chromosome theory exception

Answer 6

maternal inheritance:
- uniparental inheritance from the mother mitochondria in a zygote are from the egg cell; no mitochondria come from the sperm during fertilisation in plants, the chloroplasts are often inherited from the mother, although this is species dependednt

Question 7

Mitochondral genes are maternally inherited

Answer 7

• a male cant pass on the trait, only female passes the trait on to all her children
• mitochondrial genes encode proteins that participate in protein synthesis and energy production
• major symptoms: great fatigue