Bio DNA Replication - Genetics

Why is DNA replication needed?

So cells after division have enough genetic material.

What does a replicated cell have over its parent?

Has 2x more DNA than the parent cell.

What kind of process is DNA Replication? Why is it that kind of process

Semiconservative process; daughter strand is made of 1 parent and 1 new strand.

In what direction must DNA replication be in?

5’ to 3’ direction.

What are the origins of replication?

Sequence that makes DNA replication.

What is a replisome?

Collection of 7 proteins in charge of DNA replication.

What happens as replisomes move away from the origins of replication?

Creates a replication bubble.

What are the characteristics of DNA replication?

5’ to 3’

Is bidirectional.

What are the features of DNA Polymerase III?

Main enzyme for DNA replication;

5’ to 3’

Needs Single stranded DNA

Can’t separate parent strand or synthesize new strands

What are the requirements of DNA polymerase III?

Free 3’ end & a single strand of DNA

What are the 3 proteins needed to provide DNA polymerase IIII w/ a single-stranded DNA or are in charge of separation of parental strands?

Helicase, SSBIs and Topoisomerase.

What does Helicase do?

Breaks the H bonds between base pairs in opposite strands.

What do Single stranded binding proteins do?

Attach to single stranded DNA to prevent reformation of H bonds (complimentary base pairs)

What does Topoisomerase do?

Relieves tension of twisting forces; cuts DNA.

What does primase do?

Lays down Short RNA stand: the primer

Polymerase III uses 3’ end of primer to continue synthesis of new DNA strand

What are the features of the leading strand?

5’ to 3’

In same direction as replication fork

Synthesized continuously

What are the features of the lagging strand?

Synthesized in opposite direction of replication fork in pieces called Okazaki fragments.

What occurs for the lagging strand with primase & polymerase III?

Primase synthesizes RNA primer for Okazaki frags

Polymerase III extends daughter strand; detaches

What does Ligase do for the lagging strand?

Closes gap between Okazaki fragments and builds phosphodiester bonds.

What is a karotype?

Photographic representation of a chromosome.

What are sister chromatids?

2 duplicated sets of paired chromosomes.

What are haploid, diploid and autosomes, and gametes?

Haploid: only 1 set of chromosomes; 1n

Diploid: chromosomes pairs of homologs; 2n

Autosomes: non sex chromosomes

Gametes: sperm/eggs; are haploid cells; fuse together during fertilization

What collectively makes up the interphase?

G1, S & G2 phases.

What is the G1 phase?

Cell commits to division; grows and organelles multiply

What occurs during the S phase?

Chromatids form & DNA is replicated.

What occurs during the G2 phase?

Proteins for sorting and division are synthesized.

What is the M phase?

Mitosis: 1 nucleus divides into 2 nuclei

Cytokinesis: cytoplasm divides into 2 daughter cells

What does the G1 checkpoint check for?

Size, nutrients & DNA damage.

What does the G2 checkpoint check for?

Correct chromosome replication.

What does the Metaphase checkpoint check for?

Chromosomal attachment to spindle apparatus.

What does the anaphase checkpoint check for?

Chromosomal separation.

What all occurs during interphase to prepare for the M phase in mitotic cell division?

Chromosomes in nucleus are replicated during S phase & are not condensed.

What is the centromere region, kinetochore structures and the spindle apparatus?

Centromere regions: location where chromatids are compacted

Kinetochore structures sort chromosomes

Spindle apparatus: organizes and sorts chromosomes

What occurs during prophase of mitosis?

Chromatids condense; nuclear envelope begins to dissolve; mitotic spindles begin to form

What occurs during prometaphase of mitosis?

Spindle apparatus is complete & attaches to chromatids

NE completely dissolves; centrosomes move to poles.

What occurs during metaphase of mitosis?

Sis. chromatids align in the middle.

What occurs during anaphase of mitosis?

Chromatids connections break; now individual chromosomes

What occurs during telophase of mitosis?

Chromosomes reach poles & decondense

Nuclear envelope reforms to produce 2 separate nuclei.

What follows mitosis & what occurs in that step?

Cytokinesis follows; 2 nuclei separated into daughter cells.

What structures from for what unique cell types during cytokinesis?

Animal cells form cleavage furrows.

Plant cells form cell plates.

What is the end product of mitotic cell division?

2 daughter cells w/ the same number of chromosomes as the mother cell.

What is meiosis?

Process by which haploid cells are produced from diploid cells.

What occurs during prophase I of Meiosis I?

NE fragments;

Homologous pairs of sis chromatids associate to form a bivalent; synapsis.

What occurs during prometaphase I of Meiosis I?

NE completely broken; spindle apparatus formed

Sis chromatids attach to kinetochore microtubules

What occurs during metaphase I of meiosis?

Bivalents align along metaphase plate in a double row.

What occurs during anaphase I of meiosis?

Bivalent connections break; not sis chromatids

Joined chromatid pairs move to 1 pole.

What occurs during telophase I of meiosis?

Sis chromatids reach poles & decondense; NE reforms

½ number of sister chromatids; 2 cells are haploid.

What is meiosis II?

Separation of sister chromatids during anaphase II.

What are key differences between mitosis & meiosis?

Mitosis creates 2 genetically identical diploid daughter cells

Meiosis reduced number of sets of chromosomes; daughter cells don’t have random mix of 3 chromosomes; each haploid daughter cell has 1 complete set of chromosomes.

When does DNA replication occur for both mitosis & meiosis?

Prior to mitosis & meiosis; not between meiosis I & II.

Why does crossing over occur commonly in meiosis but not mitosis?

During prophase of meiosis I, homologs bind to form bivalents.

What is the end product of meiosis II?

4 haploid daughter cells.

What is nondisjunction & aneuploidy?

Nondisjunction: error during mitosis/meiosis where sister chromatids don’t separate correctly.

Aneuploidy: mutation from having missing/additional copies of a chromosome.

What is particulate inheritance?

Determinants of hereditary traits are transmitted in discrete units from generations.

What are characters, variants, and traits?

Characters: features or appearances

Variants: specific forms of characters

Traits: variants for a character

What are the offspring of true breeding parents that differ in a single character?

F1 offspring; monohybrids.

What are dominant and recessive traits?

Dominant: displayed characteristics.

Recessive: masked by dominant trait.

What is the law of segregation?

2 alleles of a gamete separate during process that gives rise to gametes so each gets 1 allele.

What are genotypes & phenotypes?

Genotype: Genetic composition of an individual

Phenotype: characteristics of an individual due to genes.

What are homozygotes and heterozygotes? What kind of genotypes can they present?

Homozygote: identical sets of alleles for a gene:

Heterozygote: 2 diff sets of alleles for a gene.

What are the steps for constructing a Punnett Square?

1. Identify parent genotypes

2. Identify possible gametes

3. Male gametes for columns; rows for females

4. Fill in all possible genotypes by combining alleles

5. Determine relative proportions of genotypes.

What is the law of independent assortment?

Alleles of diff. genes assort independently during gamete formation.

What is the chromosome theory of inheritance?

Chromosomes have DNA

Chromosomes are replicated & passed on from parents to offspring & cells to cells

Nucleus of diploid cells has 2 sets of chromosomes

At meiosis each homologous pairs separate into 1 daughter nucleus

Gametes are haploid cells that combine to form diploid s during fertilization w/ each gamete transmitting 1 set of chromosomes to offspring.

What is the law of independent assortment explained by?

Independent alignment during meiosis.

How are hereditary diseases caused?

Mutation of alleles.

What are the figures/symbols of Pedigree charts?

Female: circles

Males: squares

Unaffected: non-shaded

Affected: shaded

Presumed carrier: partially shaded

How are connections shown on Pedigree charts?

Vertical lines: parent to offspring

Horizontal lines: couples

Downward projections: siblings ordered by birth.

What is true about unaffected individuals and their potential offspring?

Can produce unaffected and affected offspring.

What is Huntington’s disease?

Disorder caused by degeneration of brain cells in emotions, intellect, & movement.

What are the general sex systems?

XY in mammal

X-O in insects

ZW for birds/fish

Haplodiploid for bees

What is there to know about X-linked traits?

X-linked recessive traits are more likely in males

Many X-linked recessive alleles cause diseases in humans.

What determines maleness in mammals?

The Y chromosome.

What are the 3 tenets of cell theory?

Cells are the smallest unit of life

New cells arise from pre-existing cells

All living organisms are made up of cells

How are macromolecules assembled?

Dehydration reactions.

What is the basic structure of a plasma membrane?

Phospholipid bilayer, proteins, cholesterol and carbohydrates.

What is the same and different for nucleic acids and proteins?

Building blocks: Nucleotides vs Amino acids

Function: Genetic info storage vs structure; reactions catalysts

Shape: Double helix & single strands vs Complex 3D structures (primary to quaternary levels)

Structure: Long chains of nucleotides vs chains of amino acids

What roles do the molecules in the Central dogma of molecular biology have?

DNA: contains genetic material instructions

RNA: messenger/transporter of instructions & catalyzation

Proteins: final product of copied and used genetic material.

What is the function of enzymes in cells and why is it important?

Enzymes catalyze reactions; speeding up and regulating reactions within the body.

How are photosynthesis and cellular respiration connected?

The reactants for either reaction, is the products of the other reaction.

What advantage does the use of oxygen provide during cellular respiration?

Greater efficiency for ATP production