Quiz #4: Mitosis and Meiosis, Genetic Crosses and DNA structure replication and translation

Explain how mitosis results in genetically identical cells, use the term chromosome, chromatid and chromatin

Loose chromatins condense into chromosomes which are duplicated into sister chromatids. the chromatids then separate to create two genetically identical cells

Events of interphase

G1 - growth
S - DNA replication
G2 - preparation for cell division

Events of M phase (mitotic)

Mitosis (PPMAT) + Cytokinesis (cytoplasm divides resulting in two daughter cells)

prophase

chromosomes condense, nuclear envelope disintegrates, chromatin becomes chromosomes and miotic spindle starts to form

Prometaphase

chromosomes are now visible, consisting of two aligned identical sister chromatids

Metaphase

spindle is complete, chromosomes are at the metaphase plate

Anaphase

daughter chromosomes separate to opposite ends of cell

Telophase

Nuclei forms, chromosomes decondense, two new daughter cells

G1 checkpoint

the restriction point in mammalian cells, if it give the green light then the cell will complete S, G2, and M phases and divide. If not It will switch to a non dividing state called the G0

G2 checkpoint

makes sure DNA is replicated correctly

M check point

makes sure chromosomes are aligned before division

Cancer cell qualities

No density-dependent inhibition, no anchorage dependance, no need for growth factors, metastasize, exhibit angiogenesis, immortal

No density dependent inhibition

crowded cells don’t stop dividing

No anchorage dependance

can divide without being attached to something

No need for growth factors

make their own growth factor and convey its signal

Metastasize

spreads to other parts of the body, forming new tumors

Exhibit angiogenesis

stimulate blood vessel growth

Immortal

avoid cell death, continue to divide and multiply

Difference b/w mitosis and meiosis

• mitosis produces two identical daughter cells, meiosis produces 4 genetically diverse gametes

• Mitosis have one division of cells, meiosis is two divisions

• Mitosis daughter cells has the same number of chromosomes as parent cell, meiosis daughter cells has half

• Mitosis has four stages, meiosis has 8

• Mitosis happens in somatic cell, meiosis in germ cells

Haploid cell

a gamete that contains a single set of chromosomes (23)

Diploid cell

has two sets of chromosomes (46)

What is a crossover? Where does cross over occur in meiosis?

the exchange of genetic material b/w homologous chromosomes. Happens in prophase I of meiosis

What is synaptonemal complex?

a protein structure that helps homologous chromosomes pair and align for cross-over.

Three mechanisms that contribute to genetic variation (in the meiotic process)

Independent assortment of chromosomes, crossing over, random fertilization

Independent assortment of chromosomes

each pair of chromosomes sorts maternal and paternal homologs into daughter cells independantly of the other pairs / random chromosome distribution

Mechanism #1: Crossing over

produces recombinant chromosomes, combining DNA from each parent

Mechanism #3: random fertilization

random combination of two gametes, further increasing genetic variation

Basic structure of DNA

double helix made of 2 polynucleotide chains that run in opposite directions

Back bone of DNA

made up of sugar phosphate

DNA replication

DNA unzips and DNA polymerase adds complimentary bases to form two identical strands

Transcription

DNA is transcribed into mRNA by RNA polymerase

Translation

mRNA is translated into protein by the ribosome, with tRNA bringing amino acids

Base pairing rules

Adenine - Thymine, Cytosine - Guanine

If adenine makes up 20% of the bases in a gene, what is the percentage of thymine base? what about cytosine?

A-T, so if adenine is 20% then so is thymine, together theyre 40%
C-G, 60% left so split between those two, each 30%

Replication of DNA is described as semiconservative- what does that mean

Each new DNA molecule consists of one original stands and one newly synthesized strand

DNA helicase

enzymes that untwist the double helix at the replication forks

DNA polymerase

carries out synthesis by adding complimentary nucleotides to the growing DNA strand

DNA ligase

joins DNA strands / joins Okazaki fragments on the lagging strand

Primer

needed to initiate synthesis since it is a starting point for DNA polymerase to begin replication

DNA replication is synthesized in 5’ to 3’ direction, what does it mean?

it means the direction in which a new strand of DNA is synthesized, in the 5’ to 3’ direction, adding nucleotides to the 3’ end

Difference between leading strand and lagging strand

Leading strand synthesizes continuously and in the same direction as the replication fork, lagging strand synthesizes as a series of fragments called Okazaki fragments, away from the replication fork

What enzyme is used to synthesize RNA in transcription?

RNA polymerase

To begin transcription, RNA polymerase first binds to a _______ on DNA template strand

promoter

What is an exon?

coding region and are expressed in the protein

What is an intron?

non coding region that are transcribed into pre-mRNA

3 Modifications of RNA transcript

1. 5’ capping to protect and aid in translation

2. Poly A tail added on the 3’ which protects and stabilitzes

3. Splicing which removes introns, joins exons

What is a codon?

a three nucleotide sequence in mRNA that codes for amino acid

Name the start codon

AUG

Name three stop codons

UAA, UAG, UGA

tRNA in translation

transfers amino acids to the growing polypeptide in a ribosome

Ribosome in translation

site of translation, mRNA decoded, amino acids form polypeptide chain

P-site

holds the tRNA that carries the growing polypeptide chain

A-site

holds the tRNA that carries the next amino acid to be added to the chain

E-site

the exit site where discharged tRNA leave the ribosomes

Activated tRNA enter the _____ site of a ribosome

A site

How does translation end?

When the ribosome encounters a stop codon

three binding sites for tRNA

P Site: holds the tRNA that carries the growing polypeptide chain

A Site: holds the tRNA that carries the next amino acid to be added to the chain

E site: the exit site where discharged tRNA leave the ribosomes

Prophase I

chromosomes condense, homologous chromosomes pair up

Metaphase I

homologous pairs line up in the middle

Anaphase I

homologous chromosomes separate

Telophase I

Two nuclei form, resulting in two nuclei cells

Prophase II

chromosomes condense in both haploid cells, spindle apparatus forms

Metaphase II

sister chromatids are arranged in the middle

Anaphase II

sister chromatids separate

Telophase II

Nuclei forms, chromosomes condense, 4 new daughter cells form