Bio 1100 Passing on alleles Vocab

What is a gene?

units of hereditary information consisting of a specific nucleotide sequence

What is a gene locus?

the specific physical location of a gene on a chromosome

What is an allele?

more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

What is genotype?

the genetic constitution of  a chromosome

What is a phenotype?

the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment

What is Character?

heritable features, physical & behavioral

What is Traits?

variants of a character, controlled by genes in a particular environment

Homozygous gene locus

2 identical alleles (homo=same)

Heterozygous gene locus

2 different alleles (hetero=different)

What is a model organism?

organisms with short generation times, produce large #’s offspring, have readily distinguished traits, easy organisms to used for experiments

What organism did Mendel use?

Peas

Why was peas a good choice?

mating could be controlled

How many characters and traits did Mendel study?

7 characters and 14 traits

Some characters Mendel studied

flower color, seed color, pod shape, pod color, etc.

Traits of flower color

purple or while

Traits of pod color

green or yellow

Dominant allele

gene variant that expresses its trait even when only one copy is present, masking the effect of the recessive allele

Recessive allele

gene variant that is only expressed in the phenotype when an individual inherits two copies of it, one from each parent

Homozygous

having two identical versions of the same gene inherited one from each parent

Heterozygous

having two different versions of the same gene, one from each parent

Homozygous dominant

two identical dominant alleles for a specific gene, represented by two uppercase letters

Homozygous recessive

two identical alleles of a recessive trait for a specific gene and will express the corresponding recessive trait

P Generation

parent generation - the first group used to breed, usually true-breeding organisms

F1 Generation

offspring of the P generation

F2 Generation

offspring of the F1 Generation

True-breeding strain

population of organisms that consistently produce offspring with the same phenotype when allowed to self-pollinate, ex. BB

Hybrid strain

the offspring of two different true-breeding strains, combines the traits of both parent

Monohybrid cross

cross between two heterozygous organisms for the same trait

Dihybrid cross

cross between two heterozygous organisms for two traits, observes the inheritance of both traits at the same time

Trihybrid cross

cross between two heterozygous organisms for three traits, observes the inheritance of all three traits at the same time

Name of the egg produced that is viable

Oocyte

What did Mendel discover?

That we are not a 50% combination of our parents and that some alleles hide the effects of others

Mendel’s first hypothesis

alleles are alternative versions of genes that account for variations in inherited characters

Mendel’s second hypothesis

for each characteristic, an organism inherits two alleles, one from each parent, alleles can be different or the same

Mendel’s third hypothesis

If two alleles of an inherited pair differ, then one may determine the organism’s appearance and would be called the dominant allele, if the other has no noticeable effect then its called the recessive allele

Mendel’s fourth hypothesis

Law of segregation: a sperm or egg cell carries one allele for each inherited character because allele pairs separate from each other during meiosis

How do alleles end up in different gametes?

Crossing over during anaphase, mutation, random pair of homologous chromosomes during metaphase and random separation of 

Multiplicative Rule (AND rule)

probability of getting a plant that is homozygous recessive/dominant from a cross of two heterozygous plants

Additive Law (OR rule)

chance of an event that can occur in two OR more independent ways is the SUM of each event’s probability, getting a heterozygote from crossing two heterozygotes

Mendel’s law of independent assortment

Inheritance of one character does not affect the other, they don’t have to stay together in the same combinations

What is a testcross?

When an individual with an unknown genotype is crossed with a homozygous recessive individual to determine if the unknown parent is homozygous dominant or heterozygous

Why is a testcross performed

If the unknown is homozygous dominant then all the genotypes will have the dominant allele, so all the offspring will have the dominant phenotype

Inheritance pattern for Dependent assortment

alleles are inherited together