lecture 5- pedigree analysis, sex chromosomes, sex determination

Question 1

pedigrees

Answer 1

• analysis of inheritance in families
• typically small number of offspring
• medelian ratios rarely observed
• allow inferences concerning genotypes and predictions concerning phenotypes of offspring
• pedigree data is displayed using symbols to represent various individuals, matings and offsrping

Question 2

autosomal recessive

Answer 2

• pku
• tay-sachs
• albinism

Question 3

autosomal dominant

Answer 3

• huntington
• achondroplasia

Question 4

x-linked recessive

Answer 4

• color blindness
• hemophilia

Question 5

x-linked dominant

Answer 5

• hypophosphatemia

Question 6

wild- type

Answer 6

the genotype or the phenotype that is found in nature or a standard laboratory stock in a given organism

Question 7

mutant

Answer 7

an organism or cell carrying a mutation

Question 8

mutant allele

Answer 8

an allele differing from the allele found in the standard, or the wild type

Question 9

autosomal recessive traits

Answer 9

• usually skips a generation or generations
• males and females are both affected
• if the parents of an affected individual do not exhibit the trait, then they must be heterozygous
• rare conditions in humans
• condition is caused by defective enzyme that synthesizes melanin
• a single functional allele in the heterozygote encodes sufficient protein to generate enough melanin

Question 10

autosomal dominant traits (rare)

Answer 10

• usually does not skip a generation
• male and females are both affected
• the abnormal (mutant) is dominant
• lethal genotypes affect the frequency of the lethal alleles in a population

Question 11

sex chromosomes

Answer 11

• chromosome theory of inheritance led to understanding of sex determination
• chromosomes determining sex (or sex chromosomes) were first discovered in Protenor (bug) and grasshopper
• correlation between sex phenotypes and chromosomes
• sex chromosomes pair during meiosis like homologous autosomes
• genes in the differential region show x-linked or y-linked inheritance
• genes in the pairings show x and y-linkage

Question 12

T.H. Morgan analysis

Answer 12

• morgan knew chromosome composition differed between Drosophila males and females, and proposed a model:
• white eyes id recessive to red eyes
• chromosomes, where XX is female and XY is male. the heteromorphic chromosomes synapse and disjoin during meiosis in males
• the white color gene is located on the X chromosomes