Unit 5: Heredity

Meiosis

cell division that reduces the chromosome number by half, resulting in four genetically diverse gametes.

→ Sexual Reproduction

→ happens in 2 stages goes from 46 chromosomes to 23

→ ends up with 4 genetically unique haploid cells with HALF of the genetic info, getting the other half from the other parent during fertilization

Crossing over

exchange of genetic material between homologous chromosomes

→ occurs in prophase I of meiosis and increases genetic variation in gametes.

The law of independent assortment

Alleles on different genes will sort into gametes independently of one another during meiosis

→ This means that the inheritance of one trait will not affect the inheritance of another trait. It is one of the principles that explains genetic variation.

Allele

A form of a gene:

→ Blue eyes is an allele // Eye color is the gene

Gene

The basic unit of heredity that carries genetic information and determines traits in organisms.

Law of Segregation

The principle stating that during gamete formation, the two alleles for a trait separate, ensuring that offspring receive one allele from each parent. This explains how traits are passed down through generations.

Anaphase I

Separates Homologous Pairs

Anaphase II

Separates sister chromatids

Mitosis Functions

• Growth and repair

• Asexual Reproduction

• creates 2 identical daughter diploid cells

• only goes through one round of PMAT

• separation of sister chromatids is the ONLY form of genetic variation

Meiosis Functions

• makes gametes for sexual reproduction

• 4 Genetically unique haploid cells

• two rounds of PMAT

• independent assortment in metaphase I

• crossing over in prophase I

• separation of homologous pairs in anaphase I

• separation of sister chromatids in anaphase II

Haploid

A cell that contains one complete set of chromosomes, typically half the number found in diploid cells - Meiosis

Diploid

A cell that contains two complete sets of chromosomes, one from each parent, typically found in somatic cells - Mitosis

Incomplete dominance

Neither Allele is demonstrated physically, instead a mix between the two of them resulting in a phenotype that is a blend of the parents' traits

→ Ex: red and white flowers producing pink flowers

Co-Dominance

Scenario where both alleles are expressed and neither is dominant

→ Ex) AB blood type in humans

Phenotypic Plasticity

Ability in organisms to change phenotype depending on environmental conditions without altering genotype

Genotype

Probability of an organisms allele combo

Phenotype

Likelihood of inheriting and expressing characteristics based on genotype and environment

Di Hybrid crosses

if both parents are heterozygous, answer is most likely in the 9:3:3:1 ratio given by filling out crosses

→2^N explains the heterozygous amounts in the equation

Ex): 2²=4 meaning there will be 4 possible genotypic and phenotypic expressions ( AaBb x AaBb)

A- Brown hair // a- Blonde hair // B- Brown eyes // b- blue eyes

If 2 parents are both AaBb the possible expressions will be

1. AB- 9

2. Ab- 3

3. aB- 3

4. ab- 1

Autosomal Chromosomes

Chromosomes that are not Sex chromosomes and are involved in determining most of an individual's traits and characteristics

Sex-Linked

Traits associated with either the X and Y chromosomes that are inherited differently based on the sex of the individual, often showing different expression patterns in males and females.