Inheritance

Question 1

Phenotype

Answer 1

An observable or measurable feature of an organism
- anatomical
- biochemical
- behavioral
* can be almost anything

Question 2

Genotype

Answer 2

The genetic makeup of an individual
- overall
- variants at a specific locus

Question 3

Can an organism carry genetic information that is not observable?

Answer 3

YES; genotype is not always expressed in the phenotype!

Question 4

Mendels experimental design

Answer 4

Peas
- self-fertilization
- created true-breeding strains (he was sure that phenotype corresponded directed to the genotype)
- he recorded the pedigree (parent and offspring relationships through many generations)
- the pea traits have two types (yellow and green)
- he had a large sample
- he repeated his experiment

Question 5

Mendel’s Postulate 1: Hereditary characteristics are controlled by particulate unit factors that exist in pairs in individual organisms

Answer 5

There are units of inheritance in the form of particles (chromosomes)
- they are paired (one from each parent)
* these units of inheritance can have different versions

Question 6

Alleles

Answer 6

Different versions of genetic information

Question 7

Locus

Answer 7

The location of genetic information

Question 8

Homozygous

Answer 8

Both copies of genetic information have the same allele

Question 9

Heterozygous

Answer 9

Each copy of genetic information has a different allele

Question 10

Mendels Law 2: Dominance- when an individual has two different unit factors responsible for a characteristic, only one is expressed; that unit factor is dominant over the other, which is recessive

Answer 10

One allele can cover up the expression of the other

Question 11

Dominant

Answer 11

Allele that we can observe in the phenotype

Question 12

Recessive

Answer 12

An allele that is in the genotype but not observable in the phenotype

Question 13

Polygenic

Answer 13

Descriptor for a phenotypic trait that is influenced by more than one gene

Question 14

Pleiotropic

Answer 14

Descriptor for a gene that affects more than one phenotypic trait

Question 15

Sexual reproduction combines…

Answer 15

genetic information from two haploid gametes

Question 16

Mendels Law 3: Law of Segregation

Answer 16

The paired units of inheritance (chromosomes) segregate and each sex cell receives one copy or the other with EQUAL likelihood

Question 17

What helps us understand law of segregation?

Answer 17

Punnet squares help us answer this question: if these two specific individuals breed, what is the expected proportion of genotypes and phenotypes in the resulting generation?

Question 18

Mendels Law 4: Law of Independent Assortment

Answer 18

Chromosomes get split up into gametes independently
- the segregation of any given pair of chromosomes does not affect segregation in other pairs of chromosomes, so that a gamete with “maternal” chromosome 1 will not necessarily contain “maternal” chromosome 2

Ex. the wrinkled-ness of the peas could get separated from the green-ness
- means that one person has the potential to generate over 8 million different possible gametes

Question 19

Law of Independent Assortment

Answer 19

When genes are on different chromosomes
- every combination of alleles is possible
- every combination of alleles is equally likely (same frequencies)

Question 20

When multiple genes are on the same chromosome, they will tend to be…

Answer 20

Inherited together
- linkage
- Genes A, T, and S are all linked but there are exceptions

Question 21

Chromosomal mis-segregation (nondisjunction errors)

Answer 21

Down syndrome is fairly common in human populations
- extra chromosome 21

XXX syndrome is also fairly common and is one of many ways that people can be intersex

Turner syndrome is the inverse example: a person with only ONE X chromosome