bio

homologous chromosomes

homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure

Autosomes

Any chromosome that is not a sex chromosome

sex chromosomes

One of the 23 pairs of chromosomes in the human, contains genes that will determine the sex of the individual.

Haploid

(genetics) an organism or cell having only one complete set of chromosomes

Diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number

somatic cells

Any cells in the body other than reproductive cells

Gametes

sex cells

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

independant assortment

The random seperation of the Homologous Chromosomes.

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number

Trisomy

3 copies of a chromosome

Allele

Different forms of a gene

Gene

A segment of DNA on a chromosome that codes for a specific trait

dominant allele

An allele whose trait always shows up in the organism when the allele is present.

recessive allele

An allele that is masked when a dominant allele is present

Homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

complete dominance

a relationship in which one allele is completely dominant over another BB=brown Bb=brown bb=white

incomplete dominance

Situation in which one allele is not completely dominant over another allele BB=brown Bb=light brown bb=white

Codominance

A condition in which neither of two alleles of a gene is dominant or recessive. BB=brown Bb= brown and white bb=white

sex-linked traits

Traits controlled by genes located on sex chromosomes.

multipule alleles

A gene that has more than two alleles

How many haploid cells do humans have?

23

How many diploid cells do humans have?

46

nonhomologous chromosomes

chromosomes that do not match because they have different sets of genes

interphase 1

the stage of meiosis 1 when the cell duplicates its chromosomes

prophase 1

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad

metaphase 1

Paired homologous chromosomes line up across the center of the cell(independant assortment)

anaphase 1

homolouges are seperated and move to opposite sides of the cell

telophase 1

two distinct ends of the cell form with one set of DNA on each side

prophase 2

begins with 2 daughter cells that arnt identical, DNA condenses into visable chromosomes

metaphase 2

sister chromatids line up along the center of the cell

anaphase 2

sister chromatids separate and move to opposite poles

telophase 2

A nuclear membrane forms around the chromosomes in each of the 4 new cells.

duplicated chromosome

2 sister chromatids attached by a centromere

unduplicated chromosome

a single linear strand of a chromosome.

The purpose of meiosis is to

produce gametes

Karyotypes are

the number and types of chromosomes in a eukaryotic cell