Topic 3 – Genetics-Genome

Question 1

what is DNA?

Answer 1

double stranded polymer of nucleotides, wound to form a double helix

Question 2

what are monomers of DNA

Answer 2

Nucleotides

Question 3

what are DNA nucleotides made off?

Answer 3

common sugar
phosphate group
one of 4 base: A, T, C, or G

Question 4

State full names of 4 bases found in nucleotides

Answer 4

Adenine
Thymine
Cytosine
Guanine

Question 5

Describe how nucleotides interact to form molecule of DNA

Answer 5

sugar and phosphate molecules join to form a sugar phosphate backbone in each DNA strand
base connected to each sugar
complementary base pairs (A pairs with T, C pairs with G) joined by weak hydrogen bonds

Question 6

define genome

Answer 6

entire genetic material of organism

Question 7

what is a chromosome

Answer 7

long coiled molecule of DNA that carry genetic information in form of genes

Question 8

define gene

Answer 8

section of DNA that codes for specific sequence of amino acids which undergo polymerisation to form protein

Question 9

describe method used to extract DNA from fruit

Answer 9

1. place piece of fruit in beaker and crush it
2. add detergent and salt, mix
3. filter mixture and collect liquid in test tube
4. pour chilled ethanol into test tube
5. DNA precipitates forming fibrous white solid
6. use glass rod to collect DNA sample

Question 10

why is detergent added to crushed fruit?

Answer 10

disrupts cell membranes, releasing DNA into solution

Question 11

why is salt added to crushed fruit?

Answer 11

salt encourages precipitation of DNA

Question 12

why is chilled ethanol added rather then water?

Answer 12

DNA is insoluble, encouraging its precipitation

Question 13

explain how a gene codes for a protein

Answer 13

sequence of 3 bases in gene forms triplet
each triplet codes for an amino acid
order of amino acids determines structure and function of protein formed

Question 14

why is folding of amino acids important in proteins such as enzymes?

Answer 14

folding of amino acids determine the shape of active site which must be highly specific to shape of its substrate.

Question 15

what is protein synthesis?

Answer 15

formation of protein from a gene

Question 16

what are 2 stages of protein synthesis

Answer 16

transcription

translation

Question 17

what does transcription involve?

Answer 17

formation of mRNA from DNA template

Question 18

outline transcription

Answer 18

1. DNA double helix unwinds
2. RNA polumrase binds to specific base sequence of non-coding DNA in front of gene and moves along DNA
3. RNA polymerase joins free RNA nucleotides to complementary bases on coding DNA strand.
4. mRNA formation complete. mRNA detaches and leaves nucleus

Question 19

describe differences between mRNA and DNA

Answer 19

mRNA is single stranded whereas DNA is double

MRNA uses U whereas DNA uses T

Question 20

why is mRNA used in translation rather then DNA?

Answer 20

DNA is too large to leave nucleus so cannot reach ribosome.

Question 21

what does translation involve?

Answer 21

ribosome joins amino acids in specific order dictated by mRNA to form protein

Question 22

outline translation

Answer 22

1. mRNA attaches to ribosome
2. ribosome reads mRNA bases in triplets, each code for one amino acid which is brought to ribosome by a tRNA molecule
3. a polypeptide chain is formed from sequence of amino acids which join together.

Question 23

how is tRNA molecule adapted to its function?

Answer 23

each tRNA molecule has anticodon which is specific to codon of amino acids that it carries.

Question 24

what is a mutation?

Answer 24

random change in base sequences of DNA which results in genetic variants.

Question 25

describe effect of gene mutation in coding DNA

Answer 25

if mutation changes amino acids sequence, protein structure and function may change
if mutation does not change amino acid sequence, there is no effect on protein structure or function

Question 26

what is non coding DNA?

Answer 26

DNA which does not code for protein but instead controls gene expression

Question 27

describe the effect of a gene mutation in non coding DNA?

Answer 27

`mutation may affect ability of RNA polymerase to bind to non coding DNA
may affect protien production and resulting phenotype of organism

Question 28

outline how work of Mendel helped scientists to develops understanding of genetics

Answer 28

Mendel studies inheritance of different phenotypes of pea plants
saw correlation between parent and offspring phenotypes
noted inheritance was determine by “units” passed on to descendants
using gene crosses, devised terms dominant and recessive

Question 29

why was mendel work overlooked?

Answer 29

scientists did not understand mendel work as there was no knowledge of genes or DNA at that time.