Genetics

Question 1

Mendel’s Early work

Answer 1

P -> Parental
F1 -> First Filial (Offspring of Parental generation)
F2 -> Second Filial (Offspring of F1)

He crossed a white and a purple flower, their offspring (F1) were 100% purple. He let F1 self-pollinate and their offspring (F2) were 75% purple and 25% white (3:1)
He concluded that purple was a dominant trait and white was recessive.

Question 2

What’s Independent Assortment?

Answer 2

When genes separate independently during the formation of gametes. Leads to variation

Question 3

Explain Dominant/Recessive Alleles

Answer 3

A dominant allele masks the appearance of another and a recessive alleles only appears when both alleles are recessive

Question 4

Explain Heterozygous, Homozygous, Purebreds and Hybrids

Answer 4

Heterozygous (Hybrid) -> Organisms that have two different alleles
Homozygous (Purebreds) -> Organisms that have a pair of identical alleles

Question 5

Genotype VS. Phenotype

Answer 5

Genotype -> Genetic make-up of an organism (TT,Tt,tt)

Phenotype -> An organisms appearance (blue eyes)

Question 6

Explain Codominace and give an example

Answer 6

A condition in which both alleles contribute to the phenotype of an organisms
Ex. Erminette Chicken, (Black + White Alleles)

Question 7

Explain Incomplete Dominance and give an example

Answer 7

A case in which one allele is not completly dominant over another allele. The heterozygous offspring are a blend of the parents phenotypes
Ex. Pink Flower (Red Flower + White Flower)

Question 8

Multiple Alleles

Answer 8

A gene that has more than two alleles

Ex. human blood types

Question 9

Polygenic Traits

Answer 9

A trait that is controlled by two or more GENES

Ex. Skin tone

Question 10

What is a Punnett Square for?

Answer 10

The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment

Question 11

In which situations do 3:1 and 9:3:3:1 ratios apply?

Answer 11

9: 3:3:1 -> Dihybrid Crosses (BbEe × BbEe)
3: 1 -> Monohybrid Cosses (Rw x Rw)

Question 12

Karyotype

Answer 12

A picture of the full set of human chromosomes
Autosomes -> First 22 pairs
Sex Chromosomes -> 23rd pair (XX or XY)

Question 13

What is Non-disjunction and how does it cause conditions such as Down’s, Kleinefelter’s and Turner Syndome

Answer 13

Non-Disjunction -> The failure of homologous chromosomes or sister chromatids to separate properly during cell division
Turners (Females, Karyotype 45) -> causes a female to inherit only one “X” chromosome from her parents
Kleinefelters (Males, Karyotype 47) -> causes a male to inherit two “X” chromosomes along with a “Y”
Downs -> Trisomy on Pair 21

Question 14

Describe Autosomal Chromosome Disorders

Answer 14

• Happens in one of the first 22 chromosomes
  Recessive -> must inherit both alleles to show disorder
  ex. Albinism, Cystic Fibrosis
  Dominant -> Only need to show one
  Ex. Huntingtons

Question 15

Sex - Linkage

Answer 15

Sex- linked Disorders are liked to sex- linked genes, which are any genes on the X and Y chromosomes
ALL SEX LINKED DISORDERS ARE X-LINKED

Question 16

Why are males more effected by sex linked disorders?

Answer 16

Because women have two chances to inherit the dominant allele meanwhile men have half the chance of getting the dominant allele

Question 17

Examples of Sex linked Disorders

Answer 17

Red/Green Colour Blindness, Hemophilia

Question 18

What do squares and circles symbolize in a pedigree and what does it mean when they’re shaded vs when they aren’t

Answer 18

Female = circle
Male = square 

Shaded means they’re affected with the disorder in question and unshaded means they aren’t