Topic 3 – Genetics-Genome Flashcards
what is DNA?
double stranded polymer of nucleotides, wound to form a double helix
what are monomers of DNA
Nucleotides
what are DNA nucleotides made off?
common sugar
phosphate group
one of 4 base: A, T, C, or G
State full names of 4 bases found in nucleotides
Adenine
Thymine
Cytosine
Guanine
Describe how nucleotides interact to form molecule of DNA
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
define genome
entire genetic material of organism
what is a chromosome
long coiled molecule of DNA that carry genetic information in form of genes
define gene
section of DNA that codes for specific sequence of amino acids which undergo polymerisation to form protein
describe method used to extract DNA from fruit
- place piece of fruit in beaker and crush it
- add detergent and salt, mix
- filter mixture and collect liquid in test tube
- pour chilled ethanol into test tube
- DNA precipitates forming fibrous white solid
- use glass rod to collect DNA sample
why is detergent added to crushed fruit?
disrupts cell membranes, releasing DNA into solution
why is salt added to crushed fruit?
salt encourages precipitation of DNA
why is chilled ethanol added rather then water?
DNA is insoluble, encouraging its precipitation
explain how a gene codes for a protein
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
why is folding of amino acids important in proteins such as enzymes?
folding of amino acids determine the shape of active site which must be highly specific to shape of its substrate.
what is protein synthesis?
formation of protein from a gene
what are 2 stages of protein synthesis
transcription
translation
what does transcription involve?
formation of mRNA from DNA template
outline transcription
- DNA double helix unwinds
- RNA polumrase binds to specific base sequence of non-coding DNA in front of gene and moves along DNA
- RNA polymerase joins free RNA nucleotides to complementary bases on coding DNA strand.
- mRNA formation complete. mRNA detaches and leaves nucleus
describe differences between mRNA and DNA
mRNA is single stranded whereas DNA is double
MRNA uses U whereas DNA uses T
why is mRNA used in translation rather then DNA?
DNA is too large to leave nucleus so cannot reach ribosome.
what does translation involve?
ribosome joins amino acids in specific order dictated by mRNA to form protein
outline translation
- mRNA attaches to ribosome
- ribosome reads mRNA bases in triplets, each code for one amino acid which is brought to ribosome by a tRNA molecule
- a polypeptide chain is formed from sequence of amino acids which join together.
how is tRNA molecule adapted to its function?
each tRNA molecule has anticodon which is specific to codon of amino acids that it carries.
what is a mutation?
random change in base sequences of DNA which results in genetic variants.
describe effect of gene mutation in coding DNA
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
what is non coding DNA?
DNA which does not code for protein but instead controls gene expression
describe the effect of a gene mutation in non coding DNA?
`mutation may affect ability of RNA polymerase to bind to non coding DNA
may affect protien production and resulting phenotype of organism
outline how work of Mendel helped scientists to develops understanding of genetics
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
why was mendel work overlooked?
scientists did not understand mendel work as there was no knowledge of genes or DNA at that time.
