Lecture 2: DNA, RNA, protein

Question 1

Deoxyribonucleic acid (DNA) does what

Answer 1

Stores genetic information in its sequence

Question 2

Ribonucleic acid (RNA) does what

Answer 2

Decodes genetic information into instructions for building proteins

Question 3

DNA is

Answer 3

DNA is a polymer
Repetition of a monomer
Nucleotides are building blocks
Polynucleotide chains

Question 4

Nucleotides are determined by

Answer 4

Phosphate group
Sugar
Nitrogenous base

Question 5

Four types of nucleotides in DNA

Answer 5

Four types of nucleotides depending on the nitrogenous base linked to the sugar
A- adenine
C-cytosine
G- guanine
T- thymine

Question 6

DNA structure is

Answer 6

Double helix
Alternating sugar and phosphate groups form the sides
Sugar – phosphate backbone
Phosphate of one nucleotide links to the sugar of the adjacent nucleotide

Question 7

Base pairing of nucleotides in DNA

Answer 7

A pairs with T
C pairs with G
Pairing produces weak attractive forces between opposite bases
Holds polynucleotide chains together
Hydrogen bonds
Base pairing occurs when the two polynucleotide chains are lined up in opposite directions
Anti-parallel

Question 8

Packaging of DNA includes

Answer 8

DNA associates with proteins to form chromosomes
DNA double helix coils around histone proteins – called nucleosome
Further folded into a thicker fiber
Additional packaging achieves chromosome structure for mitosis and meiosis
Supercoiling

Question 9

DNA replication is

Answer 9

Prior to cell division, DNA must be copied in order to provide each daughter cell with the entire genome
Requires extensive and accurate DNA replication
Key resides in complementary base pairing
Strands separate
Each strand acts as a template to produce a complementary strand
Semi-conservative replication

Question 10

What happens by DNA replication

Answer 10

Two new molecules identical to the first are produced
Each has 1 strand from the original molecule
Each has one newly made strand

Question 11

Central dogma is

Answer 11

DNA → RNA → Protein

Question 12

Transcription is

Answer 12

Coded information within DNA is copied into a complementary RNA sequence

Question 13

Translation is

Answer 13

RNA associates with ribosomes
The synthesis of the encoded protein molecule

Question 14

Information transfer is located in

Answer 14

The DNA and the site of protein synthesis are physically separated
DNA is located in the nucleus
The information carrier is nucleus

Question 15

Information transfer can cause

Answer 15

Protein synthesis occurs at ribosomes within the cytoplasm
Most genes contain the information for the production of a specific protein
Directly or indirectly leads to the expression of a particular phenotype
Purpose of genetic material is to encode the production of proteins in the correct cell, at the correct time, and in the correct amount

Question 16

RNA characteristics

Answer 16

RNA is a polymer of nucleotides
The sugar is ribose
Bases are A,G,C and U
Uracil replaces thymine
Uracil is similar to thymine and can pair with A
RNA is usually found in the single strand form
RNA is usually much shorter in sequence

Question 17

RNA transcription

Answer 17

RNA is produced in a manner similar to DNA replication
DNA template strand used for synthesis of a complementary mRNA strand

Question 18

mRNA does what

Answer 18

The information carrier from DNA to ribosome
The mRNA nucleotide sequence represents the instructions for assembly of a precise amino acid sequence
Acts as an intermediate gene expression product

Question 19

Proteins are and determined by

Answer 19

Proteins are polymers of amino acid chains
Twenty different amino acids are found within proteins
Each different protein has a specific amino acid sequence

Question 20

Polypeptide is

Answer 20

A single chain of amino acids

Question 21

Protein shape

Answer 21

a functional unit composed of one or more polypeptides in a 3-D shape

Question 22

4 levels of protein structures and what they are

Answer 22

Primary – amino acid sequence
Secondary – bending or twisting of polypeptide into repeating patterns
Tertiary – 3-D shape determined by amino acid interactions and surrounding environment
Quantiary – 2 or more polypeptides bind to form a functional protein

Question 23

How does a gene become a protein

Answer 23

A gene comprises a linear sequence of nucleotide pairs
A protein is a linear sequence of amino acids
The nucleotide sequence determines, and correlates with, the amino acid sequence
Each consecutive three nucleotide set specifies a single amino acid of the encoded protein
3 nucleotides code 1 amino acid

Question 24

The genetic code is

Answer 24

Genetic code specifies the relationship between the nucleotide sequence and the amino acid sequence
Each triplet of nucleotides codes for a specific amino acid
Known as a codon
The code is degenerate – amino acids are represented by more than one codon

Question 25

Translation on producing proteins

Answer 25

Translation involves converting the mRNA message into a polypeptide chain

Question 26

Mutation is

Answer 26

The flow of information from DNA to protein needs to be highly efficient and accurate Mutation = change in genetic material Mutations can be neutral, beneficial or detrimental A mutation can occur in any cell of the body at any time

Question 27

Mutation is determined by

Answer 27

Timing and location of mutation is critical to the severity of the effect and to whether the mutation can be passed to offspring Mutations in cells that give rise to gametes (germ-line cells) can be passed to offspring Mutations in somatic cells are not passed to offspring

Question 28

Mutation can be repaired by

Answer 28

Several dozen different enzymes exist to detect and repair structural alterations to DNA Excise damaged or mismatched nucleotides Fill the gap with the correct nucleotides Reseal the gap No system is error free

Question 29

Why can mutation not be fixed

Answer 29

Changes can escape detection and repair DNA may have errors Message in mRNA may be faulty Protein product may be changed

Question 30

Spontaneous mutations result from

Answer 30

result from abnormalities of biological processe

Question 31

Induced mutations caused by

Answer 31

caused by environmental agents that enter cell

Question 32

Mutagens are

Answer 32

chemical substances or physical agents that cause mutations

Question 33

Types of mutation changes and what happens

Answer 33

Mutations can cause 2 types of changes to a gene Base sequence is changed May be no amino acid change, one amino acid change, or shortened polypeptide One or more nucleotides are added or removed Results in a frameshift Completely different amino acid sequence is produced

Question 34

Cancer is caused by

Answer 34

Cancer is a disease characterized by uncontrolled cell division Cancer is usually an acquired condition that occurs later in life

Question 35

Carcinogens are

Answer 35

Carcinogens are agents that increase the likelihood of developing cancer Promote changes in DNA of somatic cells DNA alterations that affect cell division can lead to cancer