Ch 8/9 Chromosomes, Mitosis, and Meiosis, Genes and Inheritance

telomeres

sections of noncoding, repetitive DNA in eukaryotic cells that act as a protective cap on the tip of each chromosome.

Associated with aging: gets shorter with each cell division. cell dies when it is gone.

chromosomes in eukaryotic cells are…

linear

chromosomes in prokaryotic cells are…

circular

binary fission

the process in which prokaryotic cells divide. The daughter cell is an exact copy.

somatic cells

form the body of a multicellular organism

gametes

are sex cells ONLY

stage 0 of cell division: interphase

cell does not divide yet. Consists of 3 stages:

G1: primary growth phase.

S: synthesis. Every chromosome creates an exact copy of itself through replication.

G2: second period of growth and preparation for cell division

mitosis

the overall process in which a parent cell’s nucleus with it’s duplicated chromosomes, divides.

final stage of cell division: cytokenisis

the cytoplasm is divided into two daughter cells, each of which has a complete set of the parent cell’s DNA and other cellular structures.

DNA replication: unwinding and separation

DNA helicase (enzyme) binds and separates at the origin of the replication site, creating a replication fork (divided path)

DNA replication: reconstruction and elongation

DNA polymerase creates new strands of DNA using the exposed original strands as a template

DNA polymerase

the enzyme that synthesizes new copies of DNA in cells

apoptosis

programmed death of cells that are likely to accumulate significant DNA damage

before mitosis (term)

DNA (chromosomes) is replicated

during mitosis (term)

chromosomes condense, making moving around easier. The two copies of identical, replicated DNA are organized and divided into two new future nuclei

after mitosis (term)

the cytoplasm and other cell contents divide to make two new identical daughter cells.

after replication, chromosomes have…

two identical structures called sister chromatids, joined by a centromere.

stage 1 of cell division: prophase

sister chromatids condense, and the spindle forms

spindle

threads of cytoskeleton that attach to the centromeres of the sister chromatids and move the chromosomes around

stage 2 of cell division: metaphase

the spindle aligns replicated chromosomes in the middle

stage 3 of cell division: anaphase

the spindle pulls each pair of sister chromatids apart from one another at the centromeres, moving them to opposite sides

stage 4 of cell division: telophase

chromosomes begin to decondense, and new nuclei form

mitosis mainly occurs in the…

nucleus (def)

cancer

unrestrained cell growth and division that can damage adjacent tissues

benign tumor

non-cancerous

malignant tumor

cancerous, and can spread

test question: describe the 4 differences between mitosis and meiosis

test question: describe the 4 differences between mitosis and meiosis

asexual reproduction

occurs when a single parent produces identical offspring. No genetic diversity

sexual reproduction

produces offspring from the fusion of two reproductive cells through fertilization

meiosis (term)

General definition: cell division ONLY in sex cells. Enables organisms to produce haploid gametes

haploid cells

one copy of each chromosome

diploid cells

two copies of each chromosome

humans usually have ____ chromosomes.

46 (23 from mom and 23 from dad)

fertilization

two haploid gametes merge to create a diploid individual

before meiosis occurs…

DNA is replicated in a diploid cell

meiosis I

homologous (same) chromosomes separate

meiosis II

sister chromatids separate

stage 1 of meiosis I: prophase I (test question)

(meiosis) homologous chromosomes pair and cross over, exchanging genetic information

stage 2 of meiosis I: metaphase I

(meiosis) homologous chromosomes pair up in the center

stage 3 of meiosis I: anaphase I

(meiosis) the spindle pulls the homologous chromosomes to opposite ends of cells

stage 4 of meiosis I: telophase I

(meiosis) replicated chromosomes decondense and new nuclei begin to form

there is no ____ in mitosis, but there is in meiosis.

genetic diversity

crossing over (genetic recombination)

occurs when homologous chromosomes swap genetic info at the chiasmata

females have ____ chromosomes. (not number)

XX

males have ____ chromosomes. (not number)

XY

the ____ determines the sex of the baby.

male

sex is determined by whether a sperm donates an X or a Y chromosome to fertilize the XX egg

hermaphrodites

produce both male and female gametes (other species)

heredity

the passing of characteristics from parent to offspring through their genes.

dominant gene

does not allow other genes to express

recessive gene

only expresses itself with another recessive allele

homozygous

when offspring inherit the same allele from each parent

heterozygous

when offspring inherit a different allele from each parent

segregation (biology)

you have two copies of each gene, but each sperm or egg you produce has just one copy. One from mom, one from dad

testcross

mates an individual that has the recessive genotype with an individual with unknown genotype

pedigree

used to decipher and predict the inheritance patterns of genes

incomplete dominance

the phenotype of a heterozygote is intermediate between the phenotypes of the two homozygotes, a “mixture” (ex. white + black fur = gray fur)

codominance

heterozygous individuals show features of both homozygous phenotypes (ex. white + black fur = white fur with black spots)

human blood types have ____ alleles

three: I^A, I^B, i (recessive)

human blood types have ____ genotypes

six: I^AI^A, I^Ai, I^BI^B, I^Bi, I^AI^B, ii

human blood types have ____ phenotypes

four: A, B, AB, O

antigens

glycoproteins on the cell surface that signal “self” to other cells in the immune system

antibodies

immune system molecules in the blood stream that attack “nonself” antigens on cells

pleiotropy

one gene influences multiple, unrelated traits (ex. sickle cell)

Mendel’s Law of independent assortment

a trait does not influence the inheritance pattern for another trait; all traits are inherited independently of each other

dihybrid cross

mating two individuals who are each heterozygous for two traits

linked genes

when genes are on the same chromosome, they are often inherited together

DNA helicase

the enzyme that unwinds and separates the double-stranded DNA at the replication fork, allowing the replication process to occur.

DNA polymerase

the enzyme that synthesizes new copies of DNA in cells.