AP Biology Unit 5

Mitosis reproduction

Asexual

Miosis reproduction

sexual

Homologous chromosomes

a pair of chromosomes that carry the same genetic information, one homologous chromosome is inherited from mother, one from father forming the pair

Sister chromatids

2 identical homologous chromosomes, duplicated paternal or maternal homologous chromosome

Karyotype

A display of chromosome pairs ordered by size and length

Somatic (body) cells

Diploid or 2n, two complete sets of each chromosome, Humans: 2n=46

Gametic (sex) cells

Haploid or n, one set of each chromosome, humans (sperm and eggs): n =23

Types of chromosomes

Autosomal and sex

Autosomal chromosomes

Chromosomes that do not determine sex (humans have 22 pairs)

Sex chromosomes

X and Y, determine sex

Life cycle

Sequence of stages in the genetic history of an organism from creation to its own offspring

Meiosis

Process that creates haploid gamete cells in sexually reproducing diploid organisms, results in 4 daughter cells with half the number of chromosomes as parent cell, involves 2 rounds of divisions

Mitosis

Occurs in somatic cells, 1 division, results in 2 diploid daughter cells that are genetically identical

Meiosis events

Prophase I, Metaphase I, Anaphase I,

Meiosis: Prophase I

Synapsis and crossing over

Meiosis: Metaphase I

Tetrads line up at the metaphase plate

Meiosis: Anaphase I

homologous pairs separate

Synapsis

Homologous chromosomes condense and pair up in meiosis prophase I

Synaptonemal complex

Protein framework that holds homologous pairs together

Crossing over/recombination

DNA is exchanged between the non-sister chromatids (meiosis prophase I)

Chiasmata

Physical X shaped connections where sites of recombination/crossing over occur

Meiosis: Prophase II

No crossing over

True breeding

organisms that produce offspring of the same variety over many generations of self pollination

P generation

True breeding parental generation

F1 generation

hybrid offspring P generation

F2 generation

Offspring of the F1 generation

Principles of heredity

The law of segregation, the law of independent assortment

F2 generation ratio

3:1

Law of segregation

the two alleles for the same trait separate during gamete formation and end up in different gametes

The law of independent assortment

Genes for one trait are not inherited with genes of another trait

Cross between F1 dihybrid ratio

9:3:3:1

Pedigrees

Family tree that gives a visual of inheritance patterns of particular traits

Autosomal dominant

A pattern of inheritance where only one copy of the dominant allele is necessary for the trait to be expressed and it appears in every generation

Autosomal recessive

A pattern where two copies of the recessive allele are necessary for the trait to be expressed. This trait may skip generations.

X-linked dominant

A mode of inheritance where the trait is carried on the x chromosome and only one dominant allele is needed for the trait to be expressed

x-linked recessive

A pattern where the trait is carried on the x chromosome, and only one dominant allele is needed for the trait to be expressed

Y linked (holandric)

A trait carried on the Y chromosome affecting only males

Epistasis

The phenotypic expression of a gene at one locus affects a gene at abother locus

Polygenic inheritance

The affect of two or more genes acting on a single phenotype

Pleiotropy

When a single gene controls multiple traits, typically in multiple body systems

X-linked alleles inherited from father

Father can pass X-linked alleles to all pf their daughters but none of their sons

X-linked alleles inherited from mother

Mothers can pass X-linked alleles to both daughters and sons

If x linked trait is due to recessive allele

Females will only express trait is they are homozygous, males will express trait is the inherit it from mother

Hemizygous

Males who inherit x linked trait from mother

Duchenne muscular dystrophy

Progressive weakening of muscles

Hemophilia

Inability to properly clot blood

Color blindness

Inability to correctly see colors

X inactivation

During females’ development, due to having 2 X chromosomes, most of the x chromosomes in each cell becomes inactive, the inactive X in each cell of a female condenses into a Barr body