UNIT C - Genetics (BIO 30)

cell cycle

the period of time between one cell division and the next; consists of interphase, mitosis, and cytokinesis

mitosis

cell division that results in identical cells; used for growth and repair of organisms

meiosis

cell division that results in cells that have half the normal chromosome number (haploid gametes); also called reduction division

chromosome

a thick, rod-shaped body in the nucleus that forms when chromatin (long, stringy DNA) supercoils around balls of histone proteins in prophase of mitosis and meiosis

genetic material

DNA; contains the genes that direct the synthesis of proteins needed by the cell; exists as chromatin or chromosomes

cell division

the period of the cell cycle where the cell is actively dividing; composed of mitosis and cytokinesis stages

parent cell

a diploid somatic cell that's about to enter cell division

daughter cell

a cell that is the product of cell division

in mitosis they are identical to the mother cell, in meiosis they are not.

DNA

the genetic material contained in the nucleus in eukaryotes, and loose in the cytoplasm in prokaryotes

histones

proteins found in chromosomes that provide scaffolding for DNA so it can coil around to fit in the nucleus

chromatin

long fibers containing DNA, RNA, and proteins

(they form chromosomes when they coil around histones)

Mitosis

begins with one parent cell, and ends with two daughter cells (they are nearly identical to the parent cell).

if a unicellular organism is going through mitosis, its called binary fission (a type of reproduction).

centromere

holds the two identical sister chromatids together after the S phase of interphase, and through mitosis until anaphase

asexual reproduction

a type of reproduction where only one organism is needed instead of the usual two organisms (ex. Binary Fission, yeast, cutting)

variation

the existence of many combinations of traits/genes in populations (improves the chances that some members will survive if the environment changes)

mutation

permanent change in a cells genetic structure, often results in a new trait or feature in the organism

usually occurs to random mistakes in DNA replication, BUT can also be caused by chemical or physical mutagens

resistance

occurs when a drug removes susceptible bacteria/viruses from a population and leaves those mutants/variants that are resistant to the drug

super bugs

bacteria that are immune to many antibiotics

meiosis

after meiotic division, the cells will have half the needed genetic information. These are called Gametes.

to complete replication the gamete from one parent needs to meet another gamete from the other parent. This is known as fertilization.

(occurs during sexual reproduction)

human cells have ______ chromosomes

46 (23 pairs)

homologous chromosomes

pairs of chromosomes found in diploid organisms, they have the same size and shape and carry many different alleles (variations of genes).

there are 22 pairs, and the 23rd pair of chromosomes are sex chromosomes

autosomes

the 22 pairs of homologous chromosomes in each somatic cell

x chromosome

the longer sex chromosome

y chromosome

the shorter sex chromosome, has fewer genes than the x chromosome

locus

the specific location on a chromosome

allele

different form of the same gene occurring on homologous chromosomes

diploid

term describing a cell that contains two pairs of every chromosome

haploid

term describing a cell that contains half the amount of chromosomes than a diploid cell (parent cell)

polyploid

a cell that has more than 2 homologous chromosomes

karyotype

picture depicting chromosomes, used to identify abnormalities

nondisjunction

an error in meiosis that results in a non-separation in chromosomes

results in two chromosomes entering a gamete (produces gametes that contain an extra chromosome, or missing one)

chromatid

one half or two threadlike strands that a chromosome divides into during cell division

What are the stages in the cell cycle?

Interphase and "M" phase

What is interphase?

the stage of growth, no division happens during this time. It takes up 90% of the cell cycle

What is "M" phase?

the stage of division (stands for mitosis phase). This phase ends in cytokinesis.

Cytokinesis

the cell cycle phase after mitosis, when the cytoplasm divides into 2 separate daughter cells.

What are the phases included in interphase?

G1 (growth 1) phase, S (synthesis) phase, and G2 (growth 2) phase

What happens in the phase G1?

growing rapidly, producing proteins

What is S phase?

cell duplicates its DNA, each single chromosome makes a copy of itself and holds onto that copy and results in a double chromosome (referred to as sister chromatids)

they are joined together by the centromere

What is G2 phase?

cell gets bigger and prepares for division, organelles are replicated, undergoes a check to make sure all DNA was replicated properly

if the DNA was damaged beyond repair, the cell undergoes apoptosis (cell death)

What is M phase?

the cell will divide the sister chromatids into separate chromosomes, after this division the cell will go through cytokinesis to complete the division (into separate daughter cells)

eukaryotic cell is....

a cell with a membrane bound nucleus and organelles

the spindle apparatus is...

a structure made of spindle fibers, this is formed in Prophase to promote separation and movement of chromosomes during cell division

mutagen agent?

chemical/physical agent that has the ability to mutate DNA, increases the rate of mitosis

cellular clock

allows cells to go through a set number of cell divisions and then stop

hodgkins disease

a blood cancer of lymph tissue

anchorage dependence

property of normal cells that only allows mitosis to occur when cells are attached to a surface, not floating freely

density-dependent

property of normal cells that only allows mitosis to occur only when the cells are touching each other

What are the phases in Mitosis?

Prophase, metaphase, anaphase, and telophase

What happens in prophase?

first phase of mitosis, chromosomes appear scattered through the cell, nuclear membrane dissolves, centrioles move to opposite poles, forms a spindle between them

what happens in metaphase?

second phase of mitosis, chromosomes line up on the equator, and attach their centromeres to a spindle fiber

what happens in anaphase?

third phase, spindle fibers contract pulling the sister chromatids apart to opposite poles

what happens in telophase?

fourth phase, nuclear membranes form around the two groups of chromosomes, spindle apparatus dissolves, chromosomes decondense to become chromatin

centrioles

organizing bodies of the spindle

(as they move apart in prophase spindle fibers stretch out between centrioles to form the spindle apparatus)

what is a telomere?

section on each end of a chromosome that shortens with each miotic division

(if the telomere is too short, the cell doesn't divide anymore)

How are identical twins made?

one egg is fertilized by one sperm, but the morula splits into 2 masses that develop independently

How are fraternal twins made?

Two sperm cells fertilize two egg cells.

diploid is also known as...

2n

haploid is also know as...

n

in humans the all body cells are _______, except for gametes. Gametes are________.

diploid, haploid

ploidy

the chromosome number of a cell, or how many sets of chromosomes are present.

meiosis ll

second division of meiosis, no DNA replication in interphase

synapsis

when chromosomes find their pair in meiosis l (prophase), crossing over may occur

tetrad

formed in prophase meiosis l, the temporary bundle chromosomes form when sister chromatids find their pair.

independent assortment

one of Mendels laws of heredity, genes for different traits are passed on independently of eachother.

EX. just because you inherit brown eyes from one parent doesn't mean you'll inherit their curly hair, because these genes are passed on independently.

crossing over

occurs during meiosis l when homologous pairs and their attached sister chromatids form a tetrad, and come together in synapsis. THEY MAY BE CHOPPED BY ENYMES INTO PIECES.

When the chromosomes are reassembled sections of the mothers homologue MAY BE EXCHANGED WITH THE FATHERS, forming chromosomes with different combinations.

totipotent

cells that have not specialized or differentiated, they have the ability to form a complete organism.

interkinesis

the period of time between meiosis I and meiosis II.

prenatal genetic testing

testing of embryonic/fetal cells to determine chromosome number or gender

spermatogensis

process of producing gametes in males, occurs in walls of seminiferous tubules of testes

monosomy

offspring that only have one of a particular chromosome rather than 2, offspring that has a diploid number of 45 instead of the regular 46

trisomy

offspring that have 3 of one kind of chromosome rather than two, 47 diploid rather than 46

Major events in spermatogenesis in order....

Spermatogonium: The diploid stem cell that begins the process.

Primary spermatocytes: Formed from spermatogonia by mitosis; they enter meiosis I.

Meiosis I: The first meiotic division occurs.

Secondary spermatocytes: Haploid cells formed after meiosis I.

Meiosis II: Second meiotic division.

Spermatids: Resulting haploid cells that will mature into sperm.

binary fission

asexual cell division in prokaryotes, replication of chromosomes and DNA without the use of offspring or a partner, rapid

budding

a type of asexual reproduction, grows a new organism through mitosis, seen in plants

fragmentation

asexual form of reproduction seen in animals, similar to cutting plants (like if a worm is cut in half either sad can regenerate)

parthenogenesis

rare type of asexual reproduction, unfertilized haploid egg divides by mitosis and makes a new organism made of haploid cells.

sporophyte

the diploid multicellular stage in plants that show alternation of generations; produces haploid spores by meiosis

spore

haploid cell produced by meiosis in the sporophyte

gametophyte

a multicellular stage in alternation of generations that consists of haploid cells that split off to produce haploid gametes

conjugation

type of sexual reproduction that happens when two cells form a cytoplasm bridge and exchange genetic material

what is a trait?

a characteristic

what does pure mean?

an individual with both alleles for a trait being dominant or recessive

contrasting characteristic

a trait that has two alleles that are expressed in a different way (e.g., the trait for height in pea plants can have the contrasting characteristics of tall or short)

what is a factor?

the term used by Gregor Mendel to explain inheritance of a trait; today we use the term gene

law of segregation

the two genes that an organism has for each trait are separated during meiosis so that only one gene can enter a gamete; explains why body cells are diploid, but gametes are haploid

dominant

2 alleles are present, the one that is expressed is the dominant one

F1 generation

offspring of the P1 generation; F stands for filial generation—meaning brothers and sisters

F2 generation

offspring produced as a result of individuals of the F1 generation mating with other individuals of the F1 generation

filial

the offspring of a cross

genotype

what the genes say; two symbols that indicate which alleles the individual has for a particular trait (e.g., Tt

heterozygous

a genotype where the alleles are different (e.g.,Tt)

homozygous

a genotype where both alleles are the same (e.g. ,TT is homozygous dominant, tt is homozygous recessive)

hybrid

the offspring of two parents with different inheritable traits; often termed heterozygous

inheritable trait

a characteristic that is determined by genes, not the environment; a trait that is capable of being passed from parent to offspring

monohybrid

an organism that is heterozygous for one trait (e.g., Tt)

P1 generation

the first set of parents; parents of the F1 generation

phenotype

the observable characteristic of the organism (e.g., tall height or short height; is determined by genotype) (e.g., the Tt genotype results in a tall phenotype)

recessive

if two alleles are present, the allele that is hidden is recessive

true breeding

organisms that produce offspring that express the same trait generation after generation; organisms are homozygous for a trait