DNA and Cell Division M2

Question 1

Extraction and purification of DNA

Answer 1

1. physically break up cells to break open cell walls. 2. Add washing-up liquid to break open plasma and nuclear membranes. 3. Add salt which binds to DNA, and helps to precipitate the DNA. 4. Water bath at 60 degrees to denature the enzymes that would breakdown DNA. 5. Add protease enzyme to break down histones/proteins that the DNA bound to. 6. Add ice-cold ethanol precipitates the DNA to form visible strands.

Question 2

A gene is…

Answer 2

a section of a chromosome that codes for a specific protein from a sequence of amino acid.

Question 3

What does degenerate code mean?

Answer 3

there is more than one codon for each amino acid. ie. CCC and CCG both code for the same amino acid

Question 4

What does non-overlapping code mean?

Answer 4

means that the same letter is not used for two different codons

Question 5

What is meant by universal code?

Answer 5

the codes for amino acids are the same in all organism

Question 6

Explain why DNA replication is considered to be semi-conservative.

Answer 6

1. one strand acts as a template 2. half the nucleotides are in each in double-helix DNA so it contains half the bases of the original strand

Question 7

Why is complementary base pairing important.

Answer 7

1. reformation of H-bonds 2. allows the template strand to be transcripted in the nucleus and translated.

Question 8

Compare DNA replication and transcription

Answer 8

1. (D) Replication needs DNA polymerase whereas transcription needs RNA polymerase to join to the backbone and help bind free nucleotides. 2. (D) Replication produces identical double helix structure, transcription produces a single strand of mRNA that travels to ribosome to be copied. + different helicase enzymes, RNA v DNA nucleotides. 3. (S) DNA unwinds, using helicase enzyme. Template DNA. Complementary DMA. H-bonds.

Question 9

Describe the process of DNA replication (semi-conservative)

Answer 9

1. Semi conservative replication 2. HELIX unwinds. 3. H-BONDS break, each polynucleotide chain acts a template strand 4. free NUCLEOTIDES line up 5. COMPLIMENTARY BASE PAIRING. 6. H-BONDS reform. 7. DNA polymerase joins the backbone. 8. Phosphodiester bonds and nucleotides join together 9. each new molecule has one new strand and one original strand

Question 10

Name the stages of mitosis

Answer 10

Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Question 11

Prophase

Answer 11

Chromosomes condense, centrioles move to opposite ends of cells and nuclear envelope breaks down.

Question 12

how does genetic variation occur in meiosis

Answer 12

Independent assortment - different combos of alleles is a random alignment of chromosomes on the equator. Crossing Over - In prophase, chromatids twist around each other and parts of the swap over.

Question 13

Metaphase

Answer 13

Chromosomes aligned at the equator, chromosomes attached to the spindle via centromere

Question 14

Anaphase

Answer 14

centromeres divide, sister chromatids pulled to opposite poles by spindle fibres

Question 15

Describe each stage in the cell cycle

Answer 15

G1 phase - cells grows, new organelles and proteins are made. G1 checkpoint - cell checks for any damage to DNA before entering S - phase. S phase - cells replicate its DNA ready to divide by mitosis. G2 phase - cells keep growing and proteins need for cell division. G2 checkpoint - cell checks whether DNA has been replicated without any damage, so the cell can enter mitosis. Metaphase checkpoint - check assembly of spindle fibres and chromosomes attach correctly.

Question 16

Telophase

Answer 16

chromatids reach opposite poles and nuclear membranes reform, there are now two nuclei.

Question 17

Cytokinesis

Answer 17

cytoplasm divides to form two daughter cells that are genetically identical.

Question 18

Transcription

Answer 18

1. RNA polymerase causes DNA to unwind and H-bonds break. 2. Template strand, RNA polymerase causes free RNA nucleotides to line up via complementary base pairing to the template strand, join via condensation reaction forming mRNA. 3, mRNA leave nucleus via the nuclear pore

Question 19

Translation

Answer 19

1. mRNA attaches to ribosomes 2. tRNA molecule with anticodon attaches to the codon of mRNA via complementary base pairing. 3. a second tRNA molecule attaches to the next codon. 4. RNA causes the formation of a peptide bond between amino acids and the first tRNA molecule leaves. 5. amino acids form a chain of polypeptides

Question 20

What does mitosis produce

Answer 20

diploid (body cell). 2 genetically identical daughter cells.

Question 21

what does meiosis produce

Answer 21

haploid (contains half the number of chromosomes of normal body cell) ie gametes. 4 genetically different daughter cells

Question 22

Difference between mitosis and meosis.

Answer 22

Mitosis has 1 division, form 2 daughter cells, DC contain 2n of chromosomes, they are identical. occurs in eukaryotic cells. Meiosis had 2 divisions, 4 different DC cells are formed. Homologous chromosomes pair up and bivalents form as well as crossing over and independent assortment. Dc has n, half of original no of the chromosome, occurs in gametes.

Question 23

what is a bivalent

Answer 23

pair of homologous chromosomes

Question 24

totipotent

Answer 24

unspecialised and able to divide to give rise to any kid of body cell (include zygote and early embryo)

Question 25

pluripotent

Answer 25

unspecialised and able to divide and give rise to any kind of body cell (except extraembryonic membrane)

Question 26

multipotent

Answer 26

these cells divide and give rise to a small number of cell types.

Question 27

why is ATP an ideal molecule for providing energy?

Answer 27

1. releases energy in small amounts, so none is wasted in heat. 2. quickly hydrolysed. 3. energy currency of all cells. 4. cannot move out of cells but soluble so can move around the body in a solution

Question 28

describe the structure of ATP

Answer 28

adenine, three phosphate groups and ribose sugar

Question 29

describe the process of differentiation

Answer 29

divide by mitosis and undergo differentaion to become specialised for its jobs. Stem cells can also produce more undifferentated stem cells i.e they can renew themselves. adult stem cells are used to replace damaged cells.

Question 30

How do Parkinson’s and Alzheimer’s affect the body

Answer 30

P - Loss of a particular type of nerve cell which produces dopamine (controls movement). Stem cells regenerate dopamine-producing cells. A - Nerve cells in the brain die, stem cells will regrow healthy nerve cells.