Biology 105 Exam 3 - Cell Division, Mendellian Genetics, Sex-Linked Traits

What is a diploid?

two sets of chromosomes (one from mom and one from dad)

What is a haploid?

one set of chromosomes

Homologous pair

one chromosome of each pair came from each parent

Chromatin

loosely coiled chromosomes

Centromere

links sister chromatids together during cell division

Chromatids

½ of a chromosome (the > part of the X)

Kinetochore

found on the centromere of each chromatid, where the chromatids are tightly connected

Centrioles

help form spindle fibers

Centrosomes

composed of two centrioles

What does mitosis do?

keeps the chromosome number the same in parent and daughter cells

What does meiosis do?

reduces the number of sets of chromosomes and produces gametes

Cell cycle of mitosis

interphase, M phase

Interphase

the phase between cell divison

G1 phase

the phase immediately after cell division or fertilizaiton

S phase

the phase where DNA replicates

G2 phase

normal cell growth until mitosis

M phase

mitosis, this includes cytokinesis

Prophase

chromatin condenses into chromosomes and loses its small nucleolus

Metaphase

the spindle fibers attach to chromosomes as they line up along the equator of the cell

Anaphase

spindle fibers shorten, pulling chromatids to opposite sides of the cell

Cytokinesis

occurs in late anaphase, but is the physical process in which the two daughter cells are separated

Telophase

nuclear membrane reforms around each group of chromosomes and the chromosomes uncoil into chromatin and spindle fibers disappear

n

number of chromosomes in a haploid cell

Prophase I

chromatin condenses into chromosomes, the membrane dissolves, and the chromosomes undergo synapsis where crossing-over occurs, the synapsed chromosomes are called tetrads

Metaphase I

the tetrads line up along the equator of the cell, where the line-up can be random (independent assortment)

Anaphase I

the centromeres do not split, but the synapsed tetrads are yanked apart into the original replicated chromosomes

Telophase I

the nuclear membrane reforms, and the chromosomes turn back into chromatin. each daughter cell is now a haploid, being reduced from 2n to n

Prophase II

the same as prophase I

Anaphase II

the spindle fibers yank at the centromeres, which now pull apart the chromosomes into single chromatids onto each side of the cell

Telophase II

the membrane reforms around each of the cells, the cell is separated by cytokinesis and makes 4 cells

Phenotype

the visible appearance of the individual

Genotype

the genetic make up

Heterozygous

two alleles for a single trait are different

Homozygous

both alleles for a single trait are the same

Hemizygous

the heterogametic sex (males) only has one X chromosome and does not have 2 sets of instructions for the specific genes on the X chromosome

Gene

the part of a DNA molecule that codes for a particular physiological function

Allele

any one of several contrasting characteristics for a given trait coded by a gene

Autosome

chromosomes that are not involved in sex determination