Dna, Genes and Chromosomes

Question 1

DNA stands for what and is found where?

Answer 1

Deoxyribonucleic acid
It is usually found in the nucleus of each cell (nuclear DNA), though some can be found in the mitochondria (mtDNA)

Question 2

What does DNA contain?

Answer 2

It contains genetic information dtermining the structure of the cell and the way it functions.

Question 3

What does RNA stand for?

Answer 3

Ribonucleic Acid

Question 4

What are the two main types of the nucleic acids?

Answer 4

Dna and RNA

Question 5

DNA is a polymer, what does that mean?

Answer 5

It means it is a molecule that is made up of many repeating small units

Question 6

What are the repeating units in DNA?

Answer 6

Nucleotides

Question 7

Does does each nucleotide consist of?

Answer 7

A sugar molecule (deoxyribose in DNA)
A phosphate group
Nitrogenous Base

Question 8

What are the four nitrogen bases in the DNA molecule?

Answer 8

Adenine
Thymine
Cytosine
Guanine

Question 9

What are the pairing of the nitrogenous bases and how are they attracted to one another?

Answer 9

Pyrimidines:
Cytosine - Guanine
Purines:
Adenine - Thymine
They are attracted to one another by weak hydrogen bonds

Question 10

How is the genetic code of DNA determined?

Answer 10

By the order of the nitrogenous bases occurring.

Question 11

How many DNA molecules does a human cell’s nuclei have?

Answer 11

46

Question 12

Describe the ladder model

Answer 12

Example:
The ladder model consists of an untwisted double helix (displayed the molecule like a ladder)
The sides of the ladder (backbone) are alternating PHOSPHATE and SUGAR molecules.
The rungs are paired NITROGEN BASE molecules held together by a HYDROGEN bond

Question 13

What are histones?

Answer 13

They are proteins that provide structural support for a chromosome.
Consists of a group of eight special proteins in which DNA strands are wrapped around.

Question 14

What are chromatin?

Answer 14

The coiled DNA when it forms a tangled network in a cell that’s not dividing.

Question 15

When is the DNA called chromosomes?

Answer 15

When the cell divides causing the coiled chromatin to become even more tightly coiled.

Question 16

What is a gene?

Answer 16

It is the sections of DNA of each chromosome that code for a particular protein.

Question 17

Where does the areobic phase of respiration occur?

Answer 17

The mitochondria

Question 18

What is the small amount of the cell’s DNA found in the mitochondria called?

Answer 18

Mitochondrial DNA or mtDNA

Question 19

From what is mtDNA only passed to?

Answer 19

From mother to child

Question 20

What are the differences between DNA and mtDNA?

Answer 20

Nuclear DNA is in the form of long strands bound to proteins, the histones.
Mitochondrial DNA is in the form of small circular molecules that are not bound to proteins.

Question 21

How many molecules are there in each mitochondrion?

Answer 21

5 - 10

Question 22

What are exons?

Answer 22

They are sections of coding DNA

Question 23

What are introns?

Answer 23

They are the sections of non-coding DNA
- They are used for turning on and off stuff, as well as the beginning of things.

Question 24

Through what processes does the divison of cells occur?

Answer 24

Mitosis
Meiosis

Question 25

What is it that DNa must produce for DNA replication?

Answer 25

It must produce an exact copy of itself.

Question 26

Leading strand in DNA replication:

Answer 26

Synthesised as a single polymer in the 5' to 3' direction

Question 27

Lagging strand in DNA replication:

Answer 27

Synthesised in the 5' to 3' direction, but discontinuously against the overall direction of replication. There are gaps between what is being written.

Question 28

What are Okazaki fragment?

Answer 28

They are a series of short segments on the lagging strand.

Question 29

What enxyme separates the two strands of DNA replication?

Answer 29

Helicase

Question 30

Why is the helicase separation possible?

Answer 30

Due to the hydrogen bond between the base pairs being weak.

Question 31

How is the separated strang stabilised?

Answer 31

Single-stranded binding proteins (SSB) which attaches and helps to keep the separated strands apart.

Question 32

What does primase do?

Answer 32

It is a special RNA polymerase that synthesised an RNA chain that provides the priming end.

Question 33

Which two enzymes play important roles in the synthesis of the strands and how?

Answer 33

DNA POLYMERASE - adds the new nucleotides to the new strand DNA LIGASE - joins short sections of DNA together.

Question 34

What are replication forks?

Answer 34

Hundreds of Y-shaped regions of replicating DNA molecules where new strands are growing.

Question 35

What are replication bubbles?

Answer 35

Hundreds of replicating bubbles happen due to the fact that DNA doesn't just unzip seeminglessly, but every so often (kinda like the lagging strand)

Question 36

What is gyrase?

Answer 36

It is an enzyme that relieves stress on the DNA molecules by allowing free rotation around a single strand.

Question 37

What are RNA primers?

Answer 37

Before new DNA strands can form, there must be small pre-existing primers present to start the addition of new nucleotides (by DNA Polymerase III (can be described as the typewriter)).

Question 38

What is primase?

Answer 38

It is an enzyme that polymerises (synthesises) the RNA Primer

Question 39

What is DNA Ligase?

Answer 39

A linking enzyme that catalyses the formation of a covalent bond from the 3’ to 5’ end of joining strands.

Question 40

What is the difference between DNA polymerase iii and DNA polymerase i?

Answer 40

DNA polymerase iii - Main DNA builder DNA polymerase i - Editing, repair & primer removal (comes back to check everything).

Question 41

Further Detail on DNA polymerase 1

Answer 41

Proofreads & corrects typos Repairs mismatched bases Removes abnormal bases Repairs damage through life Reduces error rate from 1 in 10,000 to 1 in 100 million bases

Question 42

What is protein synthesis

Answer 42

The process by which cells make new proteins