Task 8 Revision

Question 1

What is the structure and organisation of DNA?

Answer 1

DNA is double stranded, it has a double helix shape. DNA has a phosphate sugar backbone and it consists of many nitrogenous bases (adenine, thymine, Guanine, and cytosine)
Organisation - normal DNA in GENOME, wraps around histones to form CHROMATIN, through cell division chromatin turns into chromatids, 2 copies of 23 types of chromatids make a chromosome.

Question 2

What is the structure of RNA?

Answer 2

RNA is single stranded and shorter, it has a phosphate sugar backbone and consists of nitrogenous bases (adenine, uracil, guanine, cytosine).

Question 3

What are the types of DNA and RNA? What is their function? and where are they located?

Answer 3

nDNA - is found in the nucleus
mtDNA - is found in the mitochondria
mRNA - is found in the nucleus, this transfers the genetic code to the ribosome
tRNA - is found in the cytoplasm, this carries the amino acids to the ribosome
rRNA - is found in the nucleolus, this creates ribosomes

Question 4

What is the role of DNA?

Answer 4

DNA is the blueprint for all life, it contains the instructions needed for an organism to develop, survive and reproduce.
DNA determines the structure and function of cells.

Question 5

What is the role of RNA?

Answer 5

RNA creates proteins through translation

Question 6

What are the 3 types of genes?

Answer 6

1. promoter gene
2. regulator gene
3. structural gene

Question 7

what do the 3 genes code for?

Answer 7

promoter genes - indicate which structural gene should be transcribed during protein synthesis, it acts as a binding site for RNA polymerase which then attaches and copies the structural gene.

Structural gene - codes to produce proteins at ribosomes.

Regulator genes - prevents transcription, they produce repressor molecules that block RNA polymerase from binding to the promoter gene.

Question 8

how do the 3 genes interact?

Answer 8

RG (on) –> PG (off) SG (off), no transcription
RG (off) –> PG (on) SG(on), yes transcription
RG (off) –> PG (off) SG (on), no transcription
RG (off) –> PG (on) SG (off), no transcription

Question 9

what is the process of DNA replication?

happy, people, die, lonely

Answer 9

1. Unwinding the DNA molecule - DNA helicase moves along the DNA strand and breaks hydrogen bonds, revealing nucleotides on the leading and lagging strand. primase then creates a sequence of nucleotides that attaches to the DNA strand and allows DNA polymerase to attach to the strand.
2. Making new DNA strands - DNA polymerase then attaches to the primer and moves in a 5’ to 3’ direction joining free nucleotides. on the leading strand the formation is continuous, on the lagging strand Okazaki fragments of DNA are made, and then joined. DNA ligase moves along the strand, reforming hydrogen bonds.
3. Rewinding the DNA molecule - each parent strand now has a complementary ‘new’ strand. DNA rewinds to form a double helix winds around histones and condenses to form chromatids. sister chromatids are joined together at the centromere and make a chromosome.

Question 10

what is the product of DNA replication?

Answer 10

The result of DNA replication is two DNA molecules consisting of one new and one old chain of nucleotides

Question 11

what enzymes are used in DNA replication?

Answer 11

happy, people, die, lonely

Helicase, Primase, DNA polymerase, Ligase

Question 12

What is protein synthesis?

Answer 12

protein synthesis is the production of proteins in the cell

Question 13

Processes occurring in Transcription

Answer 13

1. Initiating Transcription “initiation” - transcription is initiated by a chemical messenger which enters the nucleus from the cytoplasm (hormone, drug). Chemical messenger binds to the DNA at the relevant gene and forms part of the epigenome, RNA polymerase binds to the promoter site.
2. “Elongation” of mRNA strand - The RNA polymerase moves in a 5’ to 3’ direction unwinding the helix and breaking bonds. Forms a complementary mRNA strand using free nucleotides in the nucleus.
3. “Termination” of RNA polymerase - RNA polymerase reaches a stop sequence in the DNA. mRNA strand is released, it contains introns + exons and undergoes splicing before leaving the nucleus to reach the ribosome.
   DNA double helix is reformed.

Question 14

Processes occurring in Translation

Answer 14

1. Bind to ribosome - mRNA binds to a ribosome at codon ‘binding site.’ ribosomes move along the mRNA, one codon at a time. when it reaches the start codon (AUG) translation begins.
2. Translation - tRNA in the cytoplasm have complementary anti-codon for mRNA codons.
   anti-codon corresponds to a specific amino acid.
   collect correct amino acids and deposit them at the ribosome.
3. PEPTIDE bonds - amino acids delivered at the ribosome, are joined by ‘peptide’ bonds.
   1 ATP = 1 peptide bond
   form polypeptide chain
4. Stop Codon - When the ribosome reaches a stop codon, translation is complete.
   mRNA strand is released.
   Polypeptide chain sent to GOLGI APPARATUS for packaging.

Question 15

What is the difference between the epigenome and the genome?

Answer 15

The genome is the complete set of genetic material in an organism, while the epigenome is the set of chemical modifications to the DNA and DNA-associated proteins in the cell, which alter gene expression, and are heritable.

Question 16

What occurs during acetylation?

Answer 16

Acetylation alters the arrangement of the histones - loosely bound genes are active, tightly bound genes are silenced

Question 17

what is the process of acetylation?

Answer 17

• The DNA is negatively charged and the histones are positively charged, the laws of attraction mean that unlike charges attract, the DNA is coiled, therefore less, decreased transcription.
• Acetyl groups are negatively charged and attach to the histones making them more negative, the DNA and histones become more alike and begin to repel, uncoils. therefore there is more space and increased transcription.

Question 18

what is transcription?

Answer 18

Transcription is the process of copying a segment of DNA into RNA.

Question 19

what is translation?

Answer 19

Translation is the process that takes the information passed from DNA as messenger RNA and turns it into a series of amino acids bound together with peptide bonds.

Question 20

what is methylation?

Answer 20

Methylation is the addition or removal of methyl groups (CH3) between guanine and cytosine.

Question 21

What happens in methylation?

Answer 21

The addition of a methyl group silences a gene. it causes transcriptional repression by blocking the site for RNA polymerase attachment.
The removal of a methyl group using enzymes activates the gene for transcription.

Question 22

what is gene regulation?

Answer 22

Gene regulation is the process of turning genes on and off.

Question 23

How and when are epigenetic markers passed down?

Answer 23

Epigenetic markers turn genes on or off (acetylation, methylation), and imprinted tags are passed on from one generation to the next. most imprinted tags are lost during conception except for those that have been imprinted.

Question 24

how do epigenetic tags effect the gene?

Answer 24

Epigenetic tags act as a gatekeeper to a genes ‘on’ switch. chemical tags are methyl groups or acetyl groups.

Question 25

what occurs during interphase?

Answer 25

g1 - first growth phase
s - synthesis phase, DNA replication occurs
g2 - second growth phase

the quantity of DNA in the nucleus doubles.

Question 26

what occurs during prophase?

Answer 26

Centrioles become more visible and move towards the poles of the cell.
microtubules begin to radiate from the centrioles.
the nucleolus disappears and the nuclear membrane begins to break down.
the chromatin begins to condense into chromatids and forms into chromosomes.

Question 27

what occurs during metaphase?

Answer 27

the microtubule (spindle fibers) connect to the centromere of the chromosome. 
the spindle fibers contract, pulling the chromosomes into a single alignment along the equator of the cell.

Question 28

what occurs during anaphase?

Answer 28

the spindle fibers contract, and the chromatids separate at the centromere.
chromatids (aka. chromosomes) are pulled towards the poles.

Question 29

what occurs during telophase?

Answer 29

the chromatids (aka. chromosomes) reach the poles of the cell.
the nuclear membrane reforms 
the nucleolus reforms
the spindle fibers disappear 
the chromatids uncoil into chromatin.

Question 30

what occurs during cytokinesis?

Answer 30

the cytoplasm/organelles divide
a furrow forms between the cell membranes and pinches together forming 2 new cells
2 daughter cells are formed, identical to the parent cell.

Question 31

Cancer is…

Answer 31

the development of abnormal cells which are immortal in nature, and develop at a rapid rate, they result in an altered epigenome or DNA and cause uncontrollable cell division.

Question 32

what is a tumour?

Answer 32

cancer that develops its own blood supply.

Question 33

Main events of Meiosis 1

Answer 33

prophase 1 - crossover + recombination
metaphase 1 - after spindle fibres have attached to the chromosomes, they are aligned along the equator in PAIRS.
product - 2 non-identical, haploid cells containing 46 chromosomes.

Question 34

main events in meiosis 2

Answer 34

Meiosis 2 is the exact same as mitosis except the product is 4 non-identical haploid cells, containing 23 chromosomes.

Question 35

differences between mitosis and meiosis

Answer 35

MITOSIS -
applies to somatic cells.
function is to grow, repair and replace.
number of nuclear divisions = 1

MEIOSIS - 
applies to gametes (sperm, ova)
function is to produce gametes
number of nuclear divisions = 2
variation - random- arrangement, crossing over.