Mendels Monohybrid Cross and his 1st law

module 1

What determines the phenotype of a cell

the cues it has and the genotype of the cell

What are the cues that determines a phenotype

environmental and developmental

What is genetics

The understanding of the pattern of transmission of dna from parent to offspring

When does transmission occur

during anaphase 1 of meiosis

What is transmission

the transfer of alleles from parent to offspring

what occurs during anaphase 1

homologous chromosomes of both parents split into 2 different cells (gametes). The offspring then gets one random log from each parent.

Mendels first law

the law of segregation

monogenic

refers to one gene (and the alleles that make up the gene)

polygenic

refers to multiple genes ( and the alleles in the genes)

How dna is transmitted depends on its what?

Position

When would independent assortment occur

genes are on different chromosomes or far apart on the same chromosome

What is an autosome

a non sex chromosome

what is a sex chromosome

A X or Y chromosome

when would sex linkage occur

a gene is located on a sex chromosome

when would linkage occur

when genes are close together on the same chromosome

What is an model organism

one that is:

• easy to propagate

• has short generation time

• many characters to observe

• easy to record variations

• large progeny

P generation

OG parent generation (true breeds: homozygous)

F1 generation

progeny of the P generation. Hybrids (heterozygous)

F2 generation

the offspring of the F1

What is a reciprocal cross

when the sexes of the parent are switched to test if a trait is sex-linked or autosomal

Identifying a monohybrid cross:

• phenotype disappears in the F1 and reappears in the F2

  • trait that reappears is recessive

• 3:1 ratio

How many alleles can a person have for a single gene

only 2 ( 1 from each parent)

What is a testcross

cross used to find the unknown genotype of a dominant trait (could be homo. or hetero. )

How do you do a testcross

Cross parent with unknown dominant genotype to parent with homozygous recessive genotype

• progeny all dominant phenotype then the genotype= homo

  • progeny ½ dom. phenotype and ½ recessive then the genotype= hetero

phenotypic ratios

• 3:1 ratio) cross between 2 hetero parents

• 1:1 ration) cross between hetero and homo recessive parents

  • any other crosses will result in the phenotype being 100% the same

genotypic ratios

• 1:2:1 ratio) cross between two hetero parents

• 1:1 ratio) cross between hetero parent and homo (dom. or rec.) parent

When indicating a genotype is a wild type what sign is used

a +

When indicating a mutant genotype what sign is used

no plus sign (no sign)

when indicating an unknown allele what sign is used

a -