Master 110 U2

Key players in DNA replication:

Key players in DNA replication:

ENZYMES! Usually end in ase. Have the ability to speed up reactions, and build up or break down the reactions they act upon

Helicase, DNA polymerase, Primase, Ligase

Helicase

how does it do its job? (H)

unzips the two strands of DNA. It breaks throught the hydrogen bonds holding them together.

DNA polymerase uses

Replicated DNA molecules to make a new strand of DNA

Primase uses

primers,so DNA POLYMERASE knows where to start so replication can begin.

-primer made of RNA

Ligase

helps glue DNA Ogazaki fragments together.

Anatomy of DNA (Strand? Backbone?)

Double stranded helix with base pairing of a-t g-c

sugar phosphate backbone

RNA base pairs

A-U, G-C

DNA starts at a point called _____. Which is indicated by ___

origin, DNA sequences

At the origin, ____ unzips the DNA

We don't want them to re-zip, what do we use

helicase

SSB proteins (single stranded binding proteins) bind to DNA to keep them seperated

Primase makes ______ on both strands

Why is this important

RNA primers.

DNA polymerase won't know where to start.

DNA polymerase builds _____ in the _____ direction. This means that it moves in the ______ in the ____ direction. What is this strand called, and why?

new strand, 5' 3', old template strand, 3'-5'.

DNA polymerase can only build in the 4' to 3' direction

On the other end of the leading strand is the _____. What is it's issue

lagging strand. It can only be built in one direction so it keeps building 5' to 3' and leaves gaps.

How do haploid and diploid cells differ?

somatic: diploid, mitosis. Full set of chromosomes.

gametes: haploid, meiosis. Half a set of chromosomes

What are histones and how do they help package DNA?

Charges, what forms

compact it

histones are positively charged and DNA is negatively charged, when bonded forms nucleosomes.

What helps lagging strands and okazaki fragments

Ligase

At the end of replication we have ______ from _______ . What is this called

At the end of replication, we have two identical double helix DNA molecules from ONE original DNA molecule.

semi-conservative, one of the original strand and one of the new one.

Hippocrates

Each body part was packaged up in male semen in the form of molecules that were delivered to the womb and developed in utero

Aristotle

Similar to hippocrates, though that the semen was encoded for father's characteristic and menstrual fluid encoded for mother's characteristics.

Darwin

Gemmules which were molecules emitted from each body part of the parents and migrated and packaged into gametes.

Chromosomal Theory of Inheritance

chromosomes are the molecule of inheritance.

Chromosomes removed from sea urchins- cant reproduce. But what is the important part of the chromosme that influences heredity?

Hershey-Chase Experiment

Injected viruses with DNA and one with histone protein. The only group that could reproduce was the virus with DNA.

Who discovered the structure of DNA?

Rosalind Franklin's work was stolen by the white men watson and crick

Three components of a nucleotide, what can change? what happens when this changes?

-Phosphate/Sugar backbone

-nitrogenous base can change

-when changed, can form mutations

Ploidy vs Aneuploidy

Aneuplodiy occurs when there is an abnormal amount of chromosomes within a cell.

Ploidy is the number of full sets of chromosomes within a cell.

How do eukaryotic and prokaryotic cells differ regarding replication

replication points?

Eukaryotic- Linear replication, so we see multiple replication points, or bubbles.

Prokaryotic- Circular DNA. Do not have DNA wrapped around histone proteins. One replication point, in a circle.

Primer

provides starting point by giving promoter sequence of DNA. NOT a part of the DNA. Small segment made by RNA primase.

Why do cells need to divide?

reproduce, growth, development

Somatic vs sex cells

Somatic: diploid cells that divide via mitosis, two genetically identical cells, 46

sex cells: haploid cells that divide via meiosis , four unique daughter cells, 23

When do we see chromatin condensing into chromosomes?

Chromosomes conense during the cell cycle just before division (M phase)

homologous chromosomes

SOMATIC 946 chromosomes) contain two chromosomes for every type of cell, one from each parent.

EX: skin cells influenced 1/2 by parents 1/2 by parent (2 chromosomes)

stages of the cell cycle

G1, S, G2, M(mitosis or meiosis)

G1 what's happening, what are the chromosomes doing

how is it preparing for S?

Not condensed, acquiring materials needed to succeed in s phase

-copies organelles and makes molecular building blocks

S what's happening, what are the chromosomes doing

Not condensed, but replicated. Duplication of DNA. Also duplicates centrosomes to help separate DNA.

G2 what's happening, what are the chromosomes doing

Not condensed, acquiring materials needed to succeed in m phase by producing more organelles and proteins. reorganizes in preparation of M phase.

M what's happening, what are the chromosomes doing

Cells divide! Mitosis- two identical, meiosis - four unique

How does cytokinesis differ in plant cells?

A cell plate must form instead of a cleavage furrow ;)

How is the cell cycle regulated?

Systemic: secreted by cells other than those affected

Autonomous: secreted by cells that are dividing

Why is it important for gametes to divide via meiosis instead of mitosis?

Meiosis ensures that gametes will have 23 chromosomes as there are two rounds of division during meiosis versus one round of division via mitosis.

We need 23 sex cells for the next generation- if we only had the 46 somatic cells, our offspring would have too many chromosomes.

Why is there so much genetic variability across animals within the same species? (3)

I'm so unique I could C.R.I

Random fertilization: random combination of gametes

crossing over: occurs during prophase 1 of meiosis 1 homologous chromosome swap some of their DNA

forming a tetrad, making chromosomes unique

3. Independent assortment: chromosomes have a number of ways that they can order themselves at the metaphase plate (ONLY during meiosis).

asexual vs sexual

asexual- one parent gives rise to two genetically identical offspring

sexual- two parents give rise to one genetically unqiue offspring.

Law of Segregation

During MEIOSIS, ach individual that is a diploid has a pair of alleles for a particular trait (homologous chromosomes). When gametes are formed, each parent passes an allele at random.

law of independent assortment

Characters coded by genes on different chromosomes are inherited independently from one another.

Ex: hitchhikers thumb and attached ear lobes are on different chromosomes, so INDEPENDENTLY assorted.

-red hair and freckles

Recombination and genetic variability

If two genes are close, there is a higher likelihood that they will be associated.

pleoitropy

one gene affecting multiple characteristics

codominance

when two alleles are EQUALLY expressed, with neither being dominant or recessive.

-blood type AB blood type

-mosaic

incomplete dominance

a blend of dominant and recessive in the heterozygous. Dominant is not able to fully cover recessive.

-mixture

phenotypic plasticity

Ability of genotype to express more than one phentoype when exposed to different environments.

Modern Synthesis

A comprehensive theory of evolution that incorporates genetics and includes most of Darwin's ideas, focusing on populations as the fundamental units of evolution.

Homologous vs analogous structures

homologous is an organ or bone that is common in different animals and shows descent from a common ancestor.

Analogous structures are similar in structure but the organisms are not from a common ancestor.

Natural selction

-genetic variation due to mutation is random

-selection is very non-random

-variants that promote survival and reproduction are much more likely to become common than variants that don't

stabilizing selection

individuals near the center of a distribution curve have higher fitness than individuals at either end

ex: sand beetles being neither too light nor too dark

directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

ex: drought causes smaller seeds to become more prominent. Smaller-beaked birds will survive more than before.

disruptive selection

both extremes of the spectrum are favored

-white and black birds both have camouflage, grey birds do not

frameshift mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

alternative splicing

regulated process during gene expression that results in a single gene coding for multiple proteins

point mutations

mutations that affect a single base pair, resulting in a transition or transversion substitution

includes silent, missense, and silent mutations

missense mutation

a single nucleotide in a base has been replace with another nucleotide, producing a new amino acid and therefore codon.

nonsense mutation

Occurs when a nucleotide is swapped for a stop codon representing an amino acid.

silent mutation

a type of point mutation where there is a substitution in the third base of a codon, which often represents the same amino acid as the previous codon.

What is the overall central dogma of DNA-protein synthesis?

. RNA -> (transcription) -> DNA -> (translation) -> Protein

euchromatin vs heterochromatin

euchromatin: uncoiled genetic material (lighter stained) where mRNA is transcribed

heterochromatin: coiled genetic material that is transcriptionally inactive

Which of the following describes the stages of the cell cycle in order?

Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase

You are tutoring a student at the MSLC in preparation for their BIOS 110 Unit 2 Quiz. You are reviewing point mutations by having them use the codon chart you printed out to produce an amino acid sequence. They soon realize that although there was a change in the base that caused the mRNA to be different, the amino acid specific by the codon does not change. Which mutation has occurred?

silent

Under what condition is protein synthesis, or gene expression most likely to occur?

1. When the DNA is in a heterochromatin state because it is looser. 2. When the DNA is in a heterochromatin state because it is tighter. 3. When the DNA is in a euchromatin state because it is looser. 4. When the DNA is in a euchromatin state because it is tighter.

2.When the DNA is in a heterochromatin state because it is tighter. 3. When the DNA is in a euchromatin state because it is looser.

2 and 3

During protein synthesis, the terminator sequence is where the RNA polymerase disengages and the completed ____ sequence is released.

mrna

During alternate splicing what happens with the exons and introns?

the introns are revmoved from the pre-mRNA, and the exons are stuck together to form a mature mRNA that does not contain the intron sequences

transcription is promoted by ____ and inhibited by _____

Transcription is:

A. Promoted by acetylation and inhibited by methylation.

protein synthesis

the formation of proteins by using information contained in DNA and carried by mRNA

Is protein synthesis (gene expression) more likely to occur if the DNA is in a heterochromatin or a euchromatin state?

Euchromatin because need RNA polymerase and transcription factors to attached to the DNA and when DNA is in a heterochromatin form it is wound up too tightly for this attachment to occur.

In other words, euchromatin is more easily accessible for the assembly of transcriptional subunits, and DNA in this configuration has a higher rate of transcription.

What is histone acetylation and how does it influence gene expression?

Histone acetylation involves the attachment an acetyl group to histone proteins. This reduces positive charges and opens DNA up from a heterochromatin to a euchromatin form. Thus, acetylation promotes transcription of genes!

What is methylation and how does it influence gene expression?

In methylation, methyl groups are added to DNA, causing it to pack into heterochromatin form.

How can one gene encode for several different proteins?

Thanks to alternative splicing a gene can encode an array of proteins. The process of alternative splicing allows a cell to generate different mRNAs and ultimately different proteins from the same gene.

AKA- regardless of how the proteins are represented, the gene will be the same. EX: two sisters with green eyes have different proteins, but the same gene.

What is meant by RNA interference?

RNA molecules inhibit gene expression by adding small stretches of RNA to the mRNA strand, making it double stranded and preventing translation.

Locus

Location of a specific gene on a chromosome

Gene:

A section of DNA that codes for a particular protein(s)

Allele:

: Alternate versions of a gene (ex: dimples vs no dimples)

What is meant by a wild type allele and how does it differ from a mutant allele?

Wild type allele is the most commonly seen/expressed whereas the mutant allele is the alternative allele that is not as common.

How does recombination impact genetic variability?

Recombination increases genetic variability with distance between genes on chromosomes. The greater the distance between two genes the less likely they will be inherited together.

TBT Darwin's theory of evolution for funsies

Organisms arise from the natural selection of traits that increase that species ability to survive and reproduce.

What is descent with modification and what information supports it?

Species share a common ancestor, and they change over time to give rise to new species.

1.With our understanding of meiosis, we know that gametes carry one allele from each parent

2.DNA is the basis for cell functioning and interaction amongst other cells

3. Mutations can arise in DNA and modify how cells function/produce proteins

random fertilizaiton

one sperm will fertilize one egg

it is called random fertilization because the collection of genes within one gamete does not give that gamete a lesser or better chance than any of the other sperm cells.

It is not truly random because many sperm may attach to the egg but the egg chooses 1 to enter based on amount of glycoproteins on the outside of the sperm.

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

independent assortment

One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes