Transmission genetics

Question 1

Why was the pea plant a good choice as a model organism for Mendel’s studies

Answer 1

Widely diverse, can self pollinate, Model organism

Question 2

How did Ockham’s Razor apply to Mendel’s work?

Answer 2

Entities must not be multiplied without necessity and saw that simple is better and that both parents contribute to the off springs equally

Question 3

What is meant by true breeding?

Answer 3

also known as pure breeding where strains are consistently produce the same phenotype

Question 4

What are the differences between replicate, reciprocal, and test crosses?

Answer 4

• replicate: Producing hundreds or thousands of progeny , by repeating each cross several times
• reciprocal: same genotypes are crossed, but the sexes of the parents are reversed
• test crosses: crosses designed to determine the unknown of an organism

Question 5

Consider a monohybrid cross between two plants: one is tall and the other one is short. You know that tall is the recessive trait and short is the dominant trait, and you see that half the offspring is tall and half is short. What are the genotypes of the parents?

Answer 5

Tt x tt one heterozygous and one homozygous

Question 6

Explain Mendel’s two laws that were discussed in lecture.

Answer 6

• law of segregation: describes the units of heredity, their separation into gametes, and the random union of the
  gametes into progeny in predictable proportions
• law of independent assortment
  (Mendel’s second law): during gamete formation, the segregation of alleles at one gene

Question 7

What was the blending theory of inheritance and how did Mendel’s work reject it

Answer 7

It viewed the traits in offspring as an intermediate
mixture of the parental traits. example back and white cats would make gray
- particulate inheritance
rejects blending by stating that plants carry
two discrete hereditary units (particles, or alleles) for each trait, the alleles determine phenotype

Question 8

How can a geneticist determine the genotype of an individual with a dominant phenotype with one cross? What genotypes would you expect?

Answer 8

Can be determined by crossing it with a recessive phenotype.
If the individual is homozygous dominants than there will be no recessive phenotype.
- if the individual is heterozygous then some offspring with be homozygous recessive

Question 9

What is the ideal phenotypic ratio of the F2 generation in a dihybrid cross? What are the conditions that must occur for this ratio to exist?

Answer 9

phenotype- 3:1 the F2 must heterozygous

Question 10

Can a test-cross be performed in a dihybrid cross? What would you expect the F2 ratio to be?

Answer 10

Yes, 9:3:3:1

Question 11

Product law

Answer 11

an be used to predict
the frequency with which two independent events will occur simultaneously

Question 12

forked line method

Answer 12

a diagram used to determine gamete genotype and frequencies

Question 13

product rule

Answer 13

The probability of two independent events occurring at the same time uses the word AND

Question 14

Define proband

Answer 14

the person who first came of attention to the genetics

Question 15

True or false? Albinism is an example of an autosomal recessive trait, which appears equally in both sexes

Answer 15

True

Question 16

What is locus? How does this concept apply to Mendelian genetics?

Answer 16

location of a gene on a
chromosome (fixed position)
- Important if studying the dominance or recessiveness of a particular gene

Question 17

If a color-blind woman has children with a normal man, what will the phenotypes of the male and female children be?

Answer 17

All the daughters will be carriers but the sons will be colored blind

Question 18

Explain homozygosity

Answer 18

Inheriting the same alleles that make up each biological parent

Question 19

Explain heterozygosity

Answer 19

inherited different alleles from each biological parent

Question 20

Explain hemizygosity

Answer 20

existence of only one allele of a gene in an individual
- Seen with makes since they only have one “X”

Question 21

What are the patterns of Inheritance (6)

Answer 21

• autosomal dominant
• autosomal recessive
• X-linked dominant
• X-linked recessive
• mitochondria
• y-linked

Question 22

Medelian inheritance

Answer 22

Each parent contributes an allele to their offspring
- if the genotypes of the parents are known, Mendel’s 4
postulates can be used to estimate the genotypes and
phenotypes of the offspring

Question 23

Non-Mendelian Inheritance

Answer 23

Principles of Mendelian inheritance apply, but the
manifestation of the trait does not.
- Traits do not segregate in accordance with Mendel’s
postulates

Question 24

5 successful features of Mendels breeding experiments

Answer 24

1.Controlled crosses
2.Used pure-breeding strains to begin experimental controlled crosses
3.Selection of dichotomous traits
4.Quantification of results
5.Used replicate, reciprocal and test crosses

Question 25

Test cross

Answer 25

is a way to determine whether an individual displaying the dominant phenotype is homozygous or
heterozygous for that trait.

Question 26

Sum rule

Answer 26

used to calculate the probability of a generalized outcome that can be accomplished in more than one
way uses the word OR

Question 27

X-linked dominant

Answer 27

• Affected males produce all
  affected daughters but no
  affected sons
• Heterozygous females will
  have unaffected and affected
  offspring; sons and daughters
  will be equally affected

Question 28

X-linked recessive

Answer 28

• Hemizygous males and homozygous
  females are affected
• Males are more likely to be affected
• Affected males receive the allele from
  their mothers
• Affected daughters must receive the
  allele from both parents

Question 29

y-linked

Answer 29

• passed from father to son
• all traits for Y are expressed

Question 30

Autosomal recessive

Answer 30

1. Males and females have the trait in approximately equal frequency
2. Individuals who have the trait are often born to parents who do not (parents are heterozygous)
3. If both parents have the trait, all children will have it
4. The trait is not usually seen in each generation, rather it is typically seen among siblings
   5.if only one parent has the trait, a child can only have the trait if the other parent is heterozygous

Question 31

Autosomal dominant

Answer 31

1. Males and females have the trait in approximately equal
   frequency
2. Each individual who has the trait has at least one parent with
   the trait
3. Either gender can transmit the trait to a child
4. If neither parent has the trait, none of their children will have it
   If the trait is rare…
5. …those with the trait are likely heterozygous. In crosses where
   one parent has the trait and the other does not, approximately
   half the offspring will have the trait
6. …and both parents have it, they may produce children who do
   not have it (the parents are likely heterozygous)

Question 32

Telocentric

Answer 32

no p arm

Question 33

acrocentric

Answer 33

Shortest p arm

Question 34

Metacentric

Answer 34

Longer p arm

Question 34

Submetacentric

Answer 34

Medium sized p arm