UTD BIOL 2311 Exam 3 Study Set

Meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

germ line cells

the cellular lineage of a sexually reproducing organism from which eggs and sperm are derived.

Haploid

An organism or cell having only one complete set of chromosomes.

somatic cells

Any cells in the body other than reproductive cells

Gametes have ____ the chromosomes of the parent organism.

Half

Humans have _____ chromosomes, with ___ copies each, one half from each parent.

23; 2

sister chromatids

Identical copies of a chromosome; full sets of these are created during the S subphase of interphase.

In meiosis, we go from ___ to four ____ gametes.

4N > 1N

Somatic cells and gametes go through similar processes in cell cycle, but the main difference lies in the ____ phase.

M

Meiosis I

Homologous chromosomes separate

germline cells (2N)

cells that produce gametes

Sex cells go through normal cell cycle UNTIL

M phase (goes to Meiosis 1 instead)

Special thing about prophase in meiosis I

Each of homologous chromosomes find its sister homolog and bind tightly to it (called a bivalent/tetrad)

bivalent/tetrad

paired homologous chromosomes

synapsis

Pairing of homologous chromosomes; happens early in prophase

synaptonemal complex

A zipper-like protein structure that causes replicated homologs to become physically connected during prophase of meiosis I; sets the stage for crossing over.

Kinetichores

At centromere of chromosome and separate sister chromatids in meiosis I

How many kinetochores does each tetrad have?

4; 2 on each side

Tetrad directionality

Paternal and maternal face opposite directions and face opposite spindles

Meiosis II

sister chromatids separate

Gametes (1N)

sex cells

Tetrad DNA mixing

"Crossing over" Event; from paternal to maternal and vice Versa

Chiasma

site of crossing over

At the chiasmata, ____ cut DNA in adjacent maternal + paternal chromatids, and then ______ maternal DNA with the paternal DNA.

Enzymes; ligate

DNA recombination

rearrangement of DNA sequences by exchanging segments from different molecules

It's not uncommon for ________ to happen more than once along non-sister chromatids in a bivalent.

Crossing over

Three key events in meiosis

Replication during interphase, synapsis, ans crossing over

recombination nodules

protein assemblies formed on the synaptonemal complex that mark the points of crossover events and mediate the multistep process of genetic recombination between non-sister chromatids

Meiosis creates...

Gametes that have a mix of chromosomes from each of the two parents

If a diploid organism were to have just 2 different kinds of chromosomes, we'd say it...

Has a haploid number of 2

Haploid number formula

Haploid number n can make 2^n different combinations

What is the benefit of sexual reproduction?

genetic diversity

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

John Maynard Smith

"Sexual reproduction is a paradox"... asexual offspring means more babies! But less gene variation

Mistakes in Meiosis

nondisjunction

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Trisomy

3 copies of a chromosome

Every month, a woman's oocyte will...

- progress from the arrested prophase to metaphase I

- becomes shed at ovulation, still at metaphase I

- meiosis II initiated by sperm

Trisomy 21 (Down Syndrome) might be the result in older women because

Maintenance of her oocytes being at an early stage of meiosis for a long timr

Mendelian Genetics

The pattern of inheriting characteristics that follows the laws formulated by Gregor Mendel

Lamarckism

An evolutionary theory (proved false by Darwin) stating that species change over time by the use and disuse of structures and the inheritance of acquired traits.

Natural selection happens if 3 conditions are met...

- variation: individuals within a population vary in characteristics

- heritability: variable traits can be inherited

Differential reproduction; competition for food and mates lead to most fit to her more mates and resources

Allele

Different forms of a gene

Locus

Location of a gene on a chromosome

independent assortment of chromosomes

The random distribution of maternal and paternal chromosomes into gametes during meiosis.

segregation of alleles

Alleles separate and move into different haploid gamete sex cells

Anthers

Site of pollen grain production. Part of the stamen.

stigma

Receives pollen

Phenotypes in peas:

- pea shape

- pod shape

- pod color

- pod shape

- flower color

- stem length

- location of flowers

progeny

offspring

Mendel's principles of inheritance

Made Darwin's idea better understood

Benefits of Mendel using peas:

- cheap and available

- easy to propagate

- matings can be controlled by manual pollination

- lots of variation in gene lines

- true-breeding lines obtained for each of the variations

Sutton and Boveri

Both figured out what was going on in meiosis in terms of chromosomes and realized they contained DNA

Thomas Hunt Morgan

used Drosophila melangaster (fruit flies) to confirm the existence of sex-linked traits

sex-linked traits

Traits controlled by genes located on sex chromosomes.

Autosomes

Any chromosome that is not a sex chromosome

Nettie Stevens

discovered sex chromosomes

The human X chromosome has

1400 genes and 59 possible diseases

The human Y chromosome has

few genes on it and no diseases linked to it

Hemophilia

A hereditary disease where blood does not coagulate to stop bleeding; several kinase cascades cause clotting and one kinase being affected ruins EVERYTHING

XXX females

healthy, with no unusual physical features, slightly lower IQ and slightly taller

Klinefelter syndrome

A chromosomal disorder in which males have an extra X chromosome, making them XXY instead of XY; female body features and lower IQ

XYY syndrome

A chromosomal disorder in which males have an extra Y chromosome; taller, fertile, more likely to be in prison or mental institutions

OY

nonviable zygotes

Turner Syndrome

XO; webbed neck, short, undeveloped sex organs, low to normal intelligence

Barr body

A dense body formed from a deactivated X chromosome.

X inactivation

one of two X chromosomes is randomly inactivated and remains coiled as a Barr body

Crossing over rarely occurs between...

Adjacent loci; happens more often on distal loci

centimorgans (map units)

Units to measure distance of other gene loci

incomplete dominance

Situation in which one allele is not completely dominant over another allele; I.e. red and white flowers, with heterozygous pink flowers

Co-dominance

situation in which both alleles of a gene contribute to the phenotype of the organism (ex: blood types)

IB allele

codes for immunoglobulin type B antigens

IA allele

Codes for immunoglobulin type A antigens

ii allele

Codes for Ig type O antigens (O antigen structure is the biochemical precursor to all blood types)

IAIB allele

Codes for Ig type A and B antigens

Phenylketonuria (PKU gene)

a disorder related to a defective recessive gene on chromosome 12 that prevents metabolism of phenylalanine; cannot convert phenylalanine to tyrosine, which can cause stunting of nervous system and can cause mental development stunting

Heat sensitive genes

Seen in Siamese cats; genes where heat impacts certain enzyme function; ex: dark hair on Siamese caused by denatured enzymes that usually inhibit melanin production

cold sensitive genes

Seen in Arctic foxes and why fur is light in winter; cold denatures enzymes

Epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

Quantitative traits

Not discrete and goes on a spectrum; ex: height; distribution on a bell curve; rely on SEVERAL genes, each which have multiple alleluia forms

Five counter arguments to simple Mendelian observations

1) sex linkage

2) incomplete dominance

3) multiple allelism

4) environmental effects

5) quantitative traits

Friedrich Miescher

discovered nucleic acids

Oswald Avery

Discovered that the nucleic acid in DNA stores and transmits genetic information from one generation of bacteria to the next; challenged the "block polymer" DNA misconception; took up Griffith's work and thought the virulence gene had been taken up by R cells from dead S cells and found that DNA IS THE GENETIC MATERIAL

Alfred Hershey and Martha Chase

used radioactive markers and bacteriophages in experiments to show that DNA was the genetic material in cells

Frederick Griffith

Discovered transformation during an experiment that involved injecting mice with smooth S cells (with a protective protein cover), rough R cells(no protective coat) , heat-killed S cells, and heat-killed S cells with living R cells, which killed the mice; conclusion: live R strains transformed to S strains

Waring blender experiment

Blender will spin so fast, the empty virus protein shells will be sheared off; the 35S-labeled proteins remain outside of the cell during infection, while the 32P-DNA enters the cell

DNA is a ______ mechanism

Semi-conservative

Three hypothesized DNA replication mechanisms

1) semi conservative

2) conservative

3) dispersive—very impossible and not favored

Matthew Meselson and Franklin Stahl

proved Watson and Crick's hypothesis that DNA replicates in a semiconservative fashion with an ultra high speed centrifuge and "heavy" nitrogen isotope (15N) and a light isotop (14N) and created a CsCl gradient

DNA elongates from ___ to ____

5' to 3'

The 3' to 5' strand is the ______

Template strand

Arthur Kornberg

Wanted to identify the enzyme that replicated DNA; E. Coli was his model; radio labeled the dNTPs (deoxyribonucloside triphosphates); saw that polymerase only worked if the DNA was single stranded AND added a few "primers" to make partial double stranded parts

Primers

Small number of nucleotides that make the ssDNA partially double stranded so the polymerase has a place to start off on

DNA origin

Where the primase starts off the site where the primers will set

Watson strand

5' to 3' (leading)

Crick strand

3' to 5' (lagging)

Helicase

unwinds DNA

Topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands

leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

Primer made from

RNA by primase