4.1: DNA, genes & chromosomes Flashcards
What is a gene
Sequences of bases in DNA that codes for a specific polypeptide or a functional RNA
what is the sequence of bases in DNA that codes for a specific polypeptide or a functional RNA
a gene
What is the locus
position of a gene in DNA
what is the name for the position of a gene in DNA
locus
what does the sequence of bases in DNA determine
the sequence of amino acids in a polypeptide
what does the sequence of amino acids in a polypeptide determine
shape and function of a protein
what does the shape and function of a protein determine
characteristics of a cell
What is an allele
The various forms of a gene
Is prokaryotic DNA continuous or does it have a start/end?
continuous
Is eukaryotic DNA continuous or does it have a start/end?
has a start/end
what is the name for the various forms of a gene
an allele
What are homologous chromosomes
2 chromosomes with the same genes in the same loci
what are 2 chromosomes with the same genes in the same loci called
homologous chromosomes
what is a diploid
2 sets of chromosomes
what is the name for 2 sets of chromosomes
a diploid
what is the name for the number and type of chromosomes in a cell
karyotype
what is the karyotype
the number and type of chromosomes in a cell
can you have haploid homologous chromosomes?
no, only diploid
what is a bivalent
a replicated homologous pair of chromosomes
what is the name given to a replicated homologous pair of chromosomes
a bivalent
What is the genetic code
sequence of nucleotides that code for a specific polypeptide
what is the sequence of nucleotides that code for a specific polypeptide
the genetic code
how many bases are there in DNA
4
How many different amino acids are there in proteins
20
What are exons in the genetic code
coding regions
what are the coding regions in the genetic code
exons
what are introns in the genetic code
non-coding regions
what are the non-coding regions in the genetic code
introns
What is the role of a STOP codon and how does it do this
does not code for an amino acid and therefore stops the production of a protein
What is meant by ‘degenerate code’ in relation to the genetic code
each triplet codes for a specific amino acid and each amino acid may have more than one code
what is meant by ‘non-overlapping’ in relation to the genetic code
each base is only read once
what is meant by ‘universal code’ in relation to the genetic code
each triplet codes for the same amino acid in ALL organisms
what is a genome
complete set of genes in a cell/organism
what is a proteome
full set of proteins that can be made by the genome
what is it called when there is a series of 3 consecutive bases in the DNA
triplet
what is it called when there is a series of 3 consecutive bases in the mRNA
codon
what is it called when there is a series of 3 consecutive bases in the tRNA
anticodon
how many genes does mRNA code for
only one
how many strands is mRNA
single stranded
What is the relation between mRNA and DNA
As mRNA is transcribed from DNA, its codons are complementary to DNA’s triplets
what does the sequence of codons on the mRNA determine
the sequence of amino acids brought to the ribosome by tRNA
describe the structure of mRNA
relatively long helical polynucleotide
describe the structure of tRNA
single stranded folded into a ‘clover leaf’ shape and relatively small. Has an amino acid attachment site (top), and has an anticodon (bottom)
what does the anticodon on a tRNA molecule determine
determines which tRNA attaches to which mRNA
how many chromosomes are in a gamete
23 (haploid)
how many chromosomes are in a somatic cell
46 (diploid)
state how the quantity of chromosomes in a gamete differs from that in a somatic cell
half in a gamete (haploid)
What do 2 haploid gametes produce when they fertilise
a diploid cell
explain the advantage of DNA being a chemically stable molecule
has to remain the same from generation to generation
explain the advantage of mRNA being broken down relatively quickly
to be reused and avoid wasteful production of proteins
what is the main way that eukaryotic DNA differs from prokaryotic DNA in relation to proteins
Eukaryotic DNA is wrapped around histones whereas prokaryotic DNA is not associated with proteins
out of eukaryote, prokaryote and mitochondrial DNA, which of these possesses introns
only eukaryotic DNA
Name an organelle other than eukaryotic DNA, prokaryotic DNA and mitochondrial DNA, that has its own DNA
chloroplast
Describe 3 ways in which an ATP molecule differs from a nucleotide in a DNA molecule
1 - ATP has 3 phosphate groups, DNA nucleotide has 1 phosphate group
2 - ATP has ribose sugar group, DNA nucleotide has deoxyribose sugar group
3 - ATP can only have adenine base, DNA nucleotide can have 4 different nitrogenous bases (A,T,G,C)
Describe the difference in structure of a deoxyribose sugar (DNA nucleotide) and a ribose sugar (ATP)
ribose = hydroxyl group below carbon 2 (normal)
whereas deoxyribose has hydrogen atom below carbon 2