Why does a cell divide because of its size?

1. DNA doesn't grow with the cell, so as the cell gets larger, it demands more of DNA. To reduce strain, a cell must not grow anymore

2. Cells lose efficiency if too large because waste and nutrients do not move across the cell membrane.

Define Interphase (basic idea)

The "in between growth of a cell". There are 3 parts: G1, S, G2

Describe G1 phase (interphase)

Phase of cell growth.

Cell increases in size.

Cell synthesizes new proteins and organelles

Describe S Phase (interphase)

DNA replication.

DNA is synthesized and chromosomes are replicated.

2x the DNA

Describe G2 Phase (interphase)

Preparing for cell division.

Shortest of the phases

organelles and molecules for division are produced

what is the M Phase that follows interphase?

It is the cell division

follows interphase

produces 2 daughter cells. Consists of mitosis and cytokinesis

Mitosis

1st stage of cell division. It's the division of the cell nucleus. There are 4 phases

Mitosis: Prophase

Usually the longest

genetic material inside nucleus condenses and duplicated chromosomes become visible.

outside the nucleus, spindles begin to form

centromere

Where duplicated DNA molecules attach along their length

sister chromatid

Each DNA strand in the duplicated DNA chromosome

centrioles

Where spindles extend from in animal cells.

Mitosis: metaphase

Usually the shortest phase.

sister chromatids line up in the middle of the cell.

centrioles are at opposite ends, spindles connect to the centromes

mitosis: anaphase

Sister chromatids separate and move apart.

each sister chromatids is now considered an individual chromosome

chromosomes move to opposite ends of the cell

anaphase ends when the movements stops and the chromosomes are completely separated.

Mitosis: telophase (final phase)

Chromosomes begin to spread into tangle of chromatin

nuclear envelope reforms around each cluster of chromosomes

spindles begin to break a part

nucleus becomes visible in each daughter cell

mitosis is complete

Cytokinesis

Result of mitosis

splitting of 1 cell into 2.

Difference between plant and animal cells in cytokinesis?

Animal cells get furrows, and cytoplasm is eventually pinched into two equal parts. In plant cells, first a cell plate forms. Nucleus separates. Then a cell wall forms.

Genome

All the DNA in a cell

What is DNA packaged into?

Chromosomes

chromatin

Complex of DNA & protein that condenses during cell division

Somatic cells

Unreproductive cells

46 chromosomes!

Gametes

Reproductive cells

have 1/2 as many chromosomes as somatic cells

they have 23 chromosomes!

G 0 Phase

Most cells are in this phase. These cells are not replicating. Some cells never leave this phase! Like Nerve cells, heart cells.

Aster

Array of short microtubules extends from each centrosome

What does a Spindle include?

Centrosomes

spindle microtubules

the asters

kinetochores

proteins attached to centromere that links sister chromatids to mitotic spindle

part of the mitotic spindle

What is the importance of the G1 checkpoint in Interphase?

Provides the stop / go ahead signal that tells a cell to split, or not to split.

CDK

cyclin dependent kinase, adds phosphate to a protein), along with cyclins, are major control switches for the cell cycle, causing the cell to move from G1 to S or G2 to M.

What are the 2 types of regulatory proteins involved in cell cycle control?

Cyclin & Cyclin-dependent kinases (cdks) (this is an enzyme)

MPF (maturation-promoting factor) is a cyclin-cdk complex that triggers a cells passage from ___ to ___ phase

from G2 phase to M phase.

HeLa Cells

cancer cells from Henrietta that never stop replicating. They are used in research

What enables a cancer cell to grow?

It does not receive any signals to stop. It is uncontrollable regulation.

How do prokaryotes reproduce?

binary fission

binary fission

cell division in prokaryotes

the chromosome replicates and then 2 daughter chromosomes actively move apart.

the plasma membrane pinches inward, dividing the cell in 2

genetics

the scientific study of heredity and variation

heredity

the transmission of traits from one generation to the next

variation

is demonstrated by the differences in appearance that offspring show from parents and siblings

locus

a gene's specific location on a certain chromosome

gametes

reproductive cells (sperm & egg)

Gametes are Haploid! (23 chromosomes)

asexual reproduction

a single individual passes genes to its offspring without the fusion of gametes

life cycle

the generation to generation sequence of stages in the reproductive history of an organism

*males are always in life cycle. females exit at menopause

From conception to time one reproduces!

How many pairs of chromosomes do human somatic cells have?

23 pairs

23 from mom & 23 from dad

homologous chromosomes

the two chromosomes in each pair of somatic cells

* chromosomes in a homologous pair are the same length and carry the same inheritable traits

karyotype

ordered display of the pairs of chromosomes from a cell

autosomes

the chromosomes in a human that are not the sex chromosomes

diploid cell

has 2 sets of chromosomes. (2n)

for humans - the diploid # is 46 (2n = 46)

somatic cells are diploid

Meiosis reduces the number of chromosome sets from ___ to ___

diploid to haploid

meiosis results in ___ daughter cells

4

reductional division

Meiosis I results in 2 haploid daughter cells with replicated chromosomes

equational division

Meiosis II results in 4 haploid daughter cells with unreplicated chromosomes

What phase is this?

Mitosis - Interphase

What phase is this?

Mitosis - prophase

What phase is this?

anaphase - mitosis

What phase is this?

metaphase - mitosis

What phase is this?

mitosis - telophase

What phase is this?

mitosis - cytokinesis

What is a tetrad 4?

The homologous chromosomes in Meiosis 1, each a pair of sister chromatids, join up to form a tetrad

chiasma

x shaped regions in Meiosis 1, where crossing over occurs

recombinant chromatids

breaking & rejoining at the chiasma in Meiosis 1

In metaphase 1, ___ line up at the metaphase plate

tetrads

Anaphase 1 separates _____

homologous chromosomes

At the end of meiosis there are...

4 non-identical daughter cells

each with a HAPLOID set of unreplicated chromosomes

synapsis

homologous chromosomes loosely pair up, aligned gene by gene

What 3 events are unique to Meiosis and ALL occur in Meiosis 1?

1. synapsis & crossing over in Prophase 1 (homologous chromosomes physically connect and exchange information
2. in metaphase, there are tetrads instead of individual replicated chromosomes
3. Anaphase 1 homologous chromosomes separate, not sister chromatids

When does DNA replication occur in Mitosis and Meiosis?

during interphase

How many divisions occur in mitosis and meiosis?

Mitosis = 1

Meiosis = 2

How many daughter cells occur after mitosis, and what is their genetic composition?

2 - each are identical to the parent cell, with the same number of chromosomes

How many daughter cells occur after meiosis, and what is their genetic composition?

4 - each haploid; genetically different from parent cell AND each other

allele

is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent.

What are the 3 mechanisms that contribute to genetic variation?

1. independent assortment of chromosomes
2. crossing over of chromatids
3. random fertilization

What is the independent assortment of chromosomes?

1. they orient randomly at metaphase 1
2. either the maternal or paternal can go to the daughter cell

Crossing over produces _______ which combine DNA inherited from each parent

recombinant chromosomes

How do the sugars in DNA pair up? (C -A - T - G)

C - G

T - A

The sugar in DNA is

deoxyribose

The sugar in RNA is

ribose

What are the 3 major differences between RNA & DNA

DNA: double strand, has thymine (t), and deoxyribose

RNA - single strand, has uracel (u), and ribose

How do Viruses spread?

They inject their DNA into a host cell in order to replicate and produce more.

Chargaff's Rule

A bases = T bases & G bases = C bases

If asked to solve a question like -

A+C=T+G or A+G = T+C

Then you should use hypothetical numbers for the nucleotides

Example:

A = 10, Thus T = 10

C = 20, thus G = 20

Plug & Solve:

A+C = T + G

10+20 = 10+20

As long as the equation equals, then the variables above work in the combination given. Example of NOT working:

A+T = C+G

10+10 = 20+20

What kind of bonds hold DNA strands together?

hydrogen bond

DNA pairs ___ with ____

Purine with a pyrimidine

DNA replication begins...

at the origin of replication

It can only elongate in the 5 prime - 3 prime direction

Replication proceeds in ____ directions from each origin until the entire molecule is copied

both

Replication Fork

located at each end of the replication bubble. This is where new DNA strands are elongating.

helicases

are enzymes that untwist the double helix at the replication forks

single-strand binding proteins

bind to and stabilize single stranded DNA until it can be used as a template

topoisomerase

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

DNA can only be added to __ prime end

3

Primer

1. A primer is a strand of short nucleic acid sequences (generally about 10 base pairs) that serves as a starting point for DNA synthesis. It is required for DNA replication because the enzymes that catalyze this process, DNA polymerases, can only add new nucleotides to an existing strand of DNA.

Primase

enzyme starts an RNA chain and adds RNA nucleotides one at a time using the parental DNA as a template

The primer is short - and the 3' end serves as the starting point fro the new DNA strand.

DNA Polymerases

catalyze the elongation of new DNA at a replication fork.

Most require a primer & DNA template strand

Nucleotide triphosphate

each nucleotide that is added to a growing DNA strand

DNA can only elongate in the

5' to 3' direction BECAUSE nucleotides are added only to the free 3' end of a growing strand

the DNA polymerase synthesizes a _______ continuously toward the replication fork.

leading strand

to elongate the other new strand, the _____, DNA polymerase must work in the direction away from the replication fork.

lagging strand

Okazaki fragments

synthesize the lagging strand segments which join them together through DNA Ligase

mismatch repair of DNA

repair enzymes correct errors in base pairing

DNA can be damaged by...

chemicals, radioactive emissions, X-rays, UV light, and certain molecules (like in cigarette smoke)

nucleotide excision repair

a nuclease cuts out and replaces damaged stretches of DNA

telomeres

postpone the erosion of genes near the ends of DNA

*Like junk DNA, no specific coding for function

*May be connected to how we age

telomerase

enzyme that catalyzes the lengthening of telomeres in germ cells

a chromosome consists of a _____ packed together with ____.

DNA molecule; proteins

chromatin

complex of DNA and protein, found in the nucleus of eukaryotic cells

Organized in fibers

ribosomes

They are the sites of translation.

they consist of rNA and proteins. They are assemble proteins of the cell;

free floating or bound

What sugar is on RNA that is not on DNA?

Uracil

Proteins are the links between ____ & ____.

genotype & phenotype

genotype

genetic make up of an organism

phenotype

observable differences of an organism determined by genetics and environmental factors

Alleles

Alternative forms of the same gene that occupy the same location on a chromosome.

*At any given locus, there are 2 (1 on each chromosome in the pair) – you get 1 a from your mother and 1 from your father.

RNA

bridge between genes and the proteins for which the code

What is transcription?

the synthesis of RNA, directed by DNA - this produces mRNA

mRNA

Messenger RNA

What is translation of RNA?

synthesis of a polypeptide from amino acids, under the direction of mRNA

What is central dogma?

the concept that cells are governed by a cellular chain of command

DNA --> RNA --> to protein

Describe the Transcription in Prokaryotes.

DNA ---> mRNA ---> Ribosome

Describe the Transcription process in Eukaryotic Cells

DNA ---> Pre mRNA ---> mRNA ---> leave nucleus ---> ribosome ----> then to protein

What is involved in RNA Synthesis?

RNA synthesis is catalyzed by RNA Polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides

Promoter

The DNA sequence where RNA polymerase attaches

They signal the transcriptional start point

transcription unit

stretch of DNA that is transcribed ; a gene

What are the 3 stages of RNA Transcription

1. Initiation

2. Elongation

3. Termination

transcription factors

mediate the binding of RNA polymerase and the initiation of transcription

What happens in the elongation of the RNA strand?

1. as polymerase moves along the DNA, it untwists the double helix
2. nucleotides are added to the 3' end of the growing RNA molecule

What is the termination of transcription?

Eukaryotes: the polymerase continues transcription after the pre-mRNA is cleaved from the growing RNA chain; the polymerase eventually falls off the DNA

Why are the ends of mRNA altered?

1. They seem to facilitate the export of mRNA
2. They protect mRNA from hydrolytic enzymes
3. They help ribosomes attach to the 5' end

How are the ends of mRNA altered?

5' cap at one end and a poly tail at the other

RNA Splicing

removes introns and joins the exons - creating an mRNA molecule with a continuous coding sequence.

[cap] - [intron] - [exon] - [intron] - [exon] - [AAAA]

introns

junk DNA. They don't code for anything

exons

hold the code on mRNA. Left in sequence to be read after the introns are spliced out

spliceosomes

made of a variety of proteins & several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites

Alternative RNA Splicing

can make multiple proteins from 1 gene depending on what is spliced out of the sequence

Ribozymes

catalytic RNA molecules that function as enzymes and can splice RNA

Once DNA is transcribed to mRNA (messenger RNA), what are the characteristics of the instructions?

1. portable - can leave the nucleus
2. edited - (processed; only exons)
3. multiplicable (can make multiple mRNAs at a time
4. Temporary - mRNA degrades when need passes

How are the instructions for assembling amino acids into proteins encoded in DNA?

Genetic Code

What is a codon?

How information is ordered in RNA that is used to translate what protein should be made.

Codons are grouped in 3's

**determines what protein is to be made

tRNA

Transfer RNA - brings the correct Amino Acid to the Codon

anticodon

on the tRNA. Its the complementary to the codon on the mRNA

How many binding sites does tRNA have?

3

P

A

E

Describe the process of P A E on the tRNA

a = holds the tRNA that carries the next Amino Acid to be added to the chain

p = holds the tRNA

e = exit site from which tRNA leaves

Where do free ribosomes proteins go?

they function in the cytosol

Where do proteins go that are made in bound ribosomes?

endomembrane system OR they are secreted from the cell

What are the types of point mutations?

1. base-pair substitutions

2. base - pair insertions or deletions

Nucleotide - pair substitution

replaces one nucleotide and its partner with another pair of nucleotides

silent mutations

have no effect on the amino acid produced by a codon because of the "extra" 3rd spot on the codon

missense mutation

still code for an amino acid - but not the right one

nonsense mutations

bad! these change the amino acid codon into a stop codon. No proteins are then made

independent assortment

stating that when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.