Genetics Notes

Question 1

History of Genetics

Answer 1

• 1800’s: Blending……wrong!

- Modern Genetics: Particulate

Question 2

Modern Genetics: Particulate

Answer 2

• Monogenic Inheritance
• Cytogenetics
• Multifactorial

Question 3

Monogenic Inheritance

Answer 3

• Dominant, recessive, x-linked

- Easy to understand and solved with a Punnett Square, but very rare

Question 4

Cytogenetics

Answer 4

Karyotype used to visualize, easy to understand, but rare

Question 5

Multifactorial

Answer 5

• Common conditions but complex genetic traits
• Must understand entire genome and look for variants
• People are 99.6% the same
• Common variants = common diseases
• Quantatative Traits

Question 6

Who is Gregor Mendel

Answer 6

• His experiments-> bred 2 pea plants-> one tall and one short and found 3/4 offspring tall and 1/4 short.
• Discovered within genes dominant and recessive alleles
• 7 traits in pea plants
• Why pea plants? T

Question 7

Genetics

Answer 7

Studying hereditary patterns through the use of genes and how they are expressed

Question 8

F1 and F2 Generations

Answer 8

Parent tree cross and the offspring is F1 and two F1s cross to make F2

Question 9

Reginald Punnett (Mendel Statistics)

Answer 9

Made punnette square

Question 10

Chromosome vs. Gene

Answer 10

-Chromosome-> coiled up strand of DNA, the whole strand. Contains genes
Genes-> a certain section of DNA that codes for certain allels

Question 11

Alleles

Answer 11

Make up genes and codes for certain traits

Question 12

Dominant vs. Recessive

Answer 12

• When dominant is present with recessiv (Aa), only dominant is expressed
• Dom is capital, recessive is lowercase

Question 13

Homozygous vs. Heterozygous

Answer 13

Homozygous-> two dominants or two recessives that code for the same thing. (AA or aa). If homozygos dominant, dom trait is expressed, if homozygous recessive, recessive shows up. Same types of alleles

Heterozygous- A dominant and a recessive show up in genotype, but only dominant is expressed. Dif types of alleles

Question 14

Genotype vs. Phenotype

Answer 14

Genotype-Gene combo (Aa)

Phenotype- What physical trait shows up- (black hair)

Question 15

From gene to trait

Answer 15

From DNA-> (transcription) RNA-> (translation)-> Protein -> trait

Question 16

What can Karyotypes tell us? What can it

not tell us?

Answer 16

Can: gender, genetic disorders

Can’t- what look like

Question 17

Genetics Problem Rules

Answer 17

• Assign letters to represent the alleles: Cap for dom, lower case for rec
• Read problem for parent genotye. If heterozygous, cap letter first
• Solve problem with punnette square
• You must always..

Question 18

Genetics Problem Rules: you must always…

Answer 18

• Have a key for the letters
• Show the genotypes of the parents
• Show your work in a Punnett Square
• Answer what the question is asking

Question 19

Monohybrid Crosses

Answer 19

Involves a single gene where one allele is
dominant over another
- Use an upper and lower case letter
T=Tall
t=short

Question 20

Incomplete Dominance

Answer 20

Involves a single gene where neither trait is dominant over
another. Results in an intermediate expression of the trait
- Use two upper case letters
R=Red
W=White

Question 21

Dihybrid Crosses

Answer 21

-Involves two genes rather than one
-Follow the rules given in the problem, may be complete or incomplete
T=pointed wings P=pink wings
t=rounded wings p=yellow wings
TT or Tt
PP or Pp
TtPp
ttpp

Question 22

Sex-linked Traits

Answer 22

• Involves genes on the X sex chromosome
• First discovered in the early 1900’s by Thomas Hunt Morgan who was studying fruit flies.
• Most sex-linked genes are recessive which means it only takes one gene from the mother to give the male offspring (XY) the mutant trait. Females (XX) need two genes, one from each parent to have the mutant trait.
• Carrier Females: females who carry a recessive allele but do not have the recessive phenotype

Question 23

Multiple Alleles

Answer 23

-Involves a single trait that is controlled by 3 alleles (rather
than 2 which is what we are used to)
- Blood types are the most common example, O is
recessive, but A and B are both dominant
- Alleles: A, B, O

Question 24

Epistasis

Answer 24

• Involves a single trait, but two genes at different loci on a single chromosome
• Loci is the location of the gene on a chromosome
• One gene controls the trait while the other turns the first gene on or off depending on the genotype.

Question 25

Pedigress

Answer 25

• A chart used to track traits through generations
• Females are circles, Males are squares
• Shaded individuals show a trait (usually recessive)
• Generations are given roman numerals
• Individuals in generations are given numbers

Question 26

Mutations

Answer 26

-Random changes in a genome that occur during cell division and/or reproduction

Question 27

Evolution

Answer 27

-Random process controlled by mutations

Question 28

Natural Selection:

Answer 28

• Nonrandom process controlling populations

Question 29

Hardy-Weinburg

Answer 29

• Equilibrium

- If everything in population stays the same, then nothing the population will change

Question 30

Gene Pool

Answer 30

-All the different genes/alleles in an area/population

Question 31

Gene Frequency

Answer 31

-Gene percentage of how alleles are consistent or appear in the population

Question 32

Does natural selection always choose against the recessive trait

Answer 32

No, not always, it goes against the weaker gene. EX: dominant gene is getting killed off but recessive survives