Genetics

Question 1

genetic gambling

Answer 1

• For every gene that you have you inherit 2 allelses

* Assortment of each parents’ chromosomes into gametes is random

Question 2

Chromosomes and alleles

Answer 2

• When sperm+egg make a fertilized egg each gamete contributes 1 of each of our chromosomes, so the new individual has 2 copies of each chromosome aka homologous chromosomes

Question 3

recessive vs dominant

Answer 3

• Dominant: protein will be made (gene will be expressed)

* Recessive: protein will only be made if there is no dominant allele

Question 4

Haploid/diploid

Answer 4

• We have 46 chromosomes (diploid) 2 copies of each of 23 unique chromosomes (haploid)

Question 5

Homozygous

Answer 5

• If you have the same allele on both chromosomes

Question 6

heterozygous

Answer 6

• If you have different alleles on the two chromosomes

Question 7

3 ideas of Gregor Mendel

Answer 7

o rather than passing on the trait itself each parent passes on instructions for building the trait
o offspring receive 2 copies of the instructions for every trait
o the trait observed depends on the 2 sets of instructions

Question 8

3 Big ideas of Mendel

Answer 8

o	recessive/dominance
o	law of segregation
•	homologous chromosomes split apart
o	law of independent assortment
•	alleles that make it into the gamete do randomly

Question 9

mendel’s law of segregation

Answer 9

• Each gamete gets 1 copy of each gene from the parent

Question 10

Phenotype and Genotype

Answer 10

• Can be difficult to tell a genotype from the phenotype alone

Question 11

punnett squares

Answer 11

• Way of mapping out the possible offspring resulting from a match

Question 12

Autosomal-recessive traits

Answer 12

• Albinism, cystic fibrosis, hairline shape, tay sachs, Rh factor on RBCs

Question 13

Pedigree

Answer 13

• You can use a pedigree to follow a trait through a family

Question 14

Sex lnked traits

Answer 14

• Any traits inherited on either the X or Y chromosome

Question 15

X chromosome sex linked traits

Answer 15

o Interesting pattern
o Two X chromosomes for females so it could be expressed in a heterozygous way
o One X chromosome for men so it must be expressed
o X linked traits: traits that are on the X chromosome

• Males are more likely to display traits inherited on their 1 X chromosome, than females on their 2 X chromosomes

Question 16

What causes a phenotype

Answer 16

• Take single-gene trait like ear wax type/underarm odor (Gene: ABCC11)
• What could be the molecular mechanisms behind this difference in phenotype?
o Single transporter molecule that will affect secretion

Question 17

Wild type

Answer 17

prevalent allele in a population

o Usually protein in proper amount that functions normally

Question 18

mutant

Answer 18

rare in natural populations

o Often recessive

Question 19

epigenetic

Answer 19

something not coded for in the genome that controls expression of the gene

Question 20

Cystic fibrosis

Answer 20

• Mutation in a single gene for a single protein
• Protein is called cystic fibrosis transmembrane conductance regulator (CFTR), moves Cl- ions across cell membranes
• Movement of CL- affects water transport
• Effects: overly salty sweat, improper male gonadal development, thick mucus in lungs

Question 21

Pleitropy

Answer 21

• One gene-many traits
• One gene contributing to many traits
• Ex: SRY gene. One gene on Y chromosome codes for conversion of estrogen to testosterone, controls all male characteristics

Question 22

Independent assortment

Answer 22

• By tracking 2 traits at a time, Mendel discovered that the inheritance of each trait did not affect the inheritance of the other
• Thus, he hypothesized that traits were sorted into the gametes independently
• Mendel said: each gene is inherited separately, and inheritance of one does not influence inheritance of another
• Only part true: chromosomes sort independently, but each chromosome carries more than one gene
• Since genes are carried on chromosomes, and chromosomes are inherited as 1 unit, often these are often inherited together
• The closer genes are together on the chromosome, the MORE likely they are to be inherited together, because they don’t tend to get separated during crossing over

Question 23

linked genes

Answer 23

• Genes that are located on the same chromosome are more likely to be inherited together
• Due to corssing over during meiosis, homologous chromosomes can exchange pieces of chromosomes and create new combinations of alleles
• The likelihood of crossing over depends on the distance between two genes
• Genes located VERY close together are unlikely to be separated by crossing over
• Called linked genes
• Certain alleles are usually inherited together
o Red hair and freckles

Question 24

Linkage maps

Answer 24

• By charting how often two alleles were inherited together, scientists were able to map genes onto chromosomes in order!

Question 25

Incomplete dominance

Answer 25

• Heterozygote appears as an intermediate btw the two homozygotes
• In this example, the amount of protein produced is coded for by the gene
• Red flowers have A LOT of pigment
• White flowers have no pigment
• Red and white reprocude and get pink flowers

Question 26

multiple allelism

Answer 26

• Some traits are controlled by genes which have more than 2 alleles
• Gene that determines blood type
• ABO: codominance and multiple allelism

Question 27

codominance

Answer 27

• The heterozygote displays characteristics of BOTH homozygotes
• Red blood cells
o Type AB

Question 28

environmental effects

Answer 28

• The environment can affect the expression of genes, mostly through epigenetics
o Ex: skin color and identical twins

Question 29

Gene interaction

Answer 29

• Most traits are influenced by more than one gene
• Variations
o One allele of one gene could prevent expression of an allele of a different gene
o Multiple genes have additive effects on a single character

Question 30

Polygenic Trait Example: skin color

Answer 30

• More than one gene contributing to a single trait
• Controlled by 3 genes, each with 2 alleles
• Dark allele=more melanin production
• Light allele= less melanin production
• A^D or A^L, B^D or B^L, C^D or C^L
• Then, add in environmental effects