Human Genetics

Question 1

Pedigree of a Dominant and recessive allele

Answer 1

• Dominant: affected individuals are equally likely to be male and female, likely only one affected parent, half the offspring affected
• Recessive: can skip generations, males and females equally likely, may have unaffected parents, effects often result from mattings with first cousins

Question 2

Human Sex Chromosomes

Answer 2

• X is more than 150 Mb long
• Y is about 50 Mb long
• many of the genes on the X have no Y counter part

Question 3

Segregation of the Sex Chromosome

Answer 3

• anaphase 1: half the sperm have X, half have Y
• conception ratio of 1:1 female:male
• at birth 100:105, female:male

Question 4

X-Linked genes

Answer 4

• found by Morgan in 1910 by observing white and red eyed patterns in fruit flies
• All females had red eyes, only some males had white eyes when crossed with the same F1 gen

Question 5

Colour-Blindness

Answer 5

• red-green color blindness
• almost always males, males only need one copy of the gene to be mutant
• females could be heterozygous carriers
• affected males have unaffected sons, as they only transmit an X to daughters

Question 6

Genetic Linkage

Answer 6

• when genes are close on the same chromosome they are linked
• discovered by Sturtevant in Drosophila, tested to see if two traits were inherited together (linked)

Question 7

Genetic Maps

Answer 7

• frequency of recombination between a and b, b and c, a and c to determine order on the chromosome
• a and c = a and b and b and c
• one unit of distance on a map is 1% of recombination
• maximum 50 units to be x-linked

Question 8

Y-linked genes

Answer 8

• Y solely inherited from males
• SRY gene on the Y encodes a protein to trigger male development
• Y genes cannot cross over with the X chromosome
• other than maleness and some types of infertility, there are no physical y-linked traits

Question 9

Y chromosome haplotypes

Answer 9

• Y chromosomes follow a lineage in an evolutionary tree
• each unique combo of nucleotides makes up a haplotype (haploid genome)
• each geographically distinct population has a somewhat different Y haplotypes assortment

Question 10

Mitochondrial/Chloroplast DNA

Answer 10

• have their own genomes that code for enzymes
• both males an females can show a trait
• all offspring of an affected female show the trait (inherited only from mom)
• like Y haplotypes, mitochondrial haplotypes remain intact through generations
• NOT associated with the x-chromosome