DNA (Further) Flashcards
How is DNA stored in eukaryotic cells
Each chromosome (found in nucleus) is made up of 1 long DNA molecule and its associated proteins. As the DNA molecule is so long it is wound around proteins called histones. The DNA and proteins are then coiled very tightly, making a compact chromosome.
What else do histone proteins do (other than get wound up in DNA)
Help to support the DNA.
What do mitochondria and chloroplast in eukaryotic cells also have
Their own DNA. Their DNA is similar to prokaryotic DNA because its circular and shorter than DNA molecules in nucleus.
Is mitochondria and chloroplast DNA associated with histone proteins?
No
How is DNA stored in prokaryotic cells?
Prokaryotes also carry DNA as chromosomes - but they’re shorter and circular. It’s not wound around histones - it condenses to fit in the cell by supercoiling.
What is a gene and where are they contained
Contained within DNA, a gene is a sequence of DNA bases that codes for either a polypeptide or functional RNA.
What is different about each polypeptide chain
The number and order of its amino acids
What determines the order of amino acids in a particular polypeptide
The order of the bases in a gene
What is each amino acid coded for by
A sequence of 3 bases in a gene called a triplet or codon
What is the first stage of protein synthesis
DNA is copied into messenger RNA (mRNA)
What do genes that don’t code for a polypeptide code for
Functional RNA instead
What are functional RNA
RNA molecules other than mRNA, which perform special tasks during protein synthesis e.g. tRNA and ribosomal RNA (rRNA), which forms part of ribosomes.
What is the complete set of genes in a cell known as
The cells genome
What is the full range of proteins that a cell is able to produce called
It’s proteome
In eukaryotes what does a lot of the nuclear DNA do
Doesn’t code for polypeptides
What do even genes that do code for polypeptides contain
Sections that don’t code for amino acids
What are the sections of DNA that don’t code for amino acids in genes that code for polypeptides called
Introns
How many introns can be in a gene and what is there purpose
Can be several introns and there purpose isn’t known for sure
What happens to introns in eukaryotes during protein synthesis
They are removed so they don’t affect the amino acid order.
Does prokaryotic DNA have introns
No
What are the bits of a gene that do code for amino acids called
exons
What does eukaryotic DNA contain outside of genes
Regions of multiple repeats, these are DNA sequences that repeat over and over. E.g. CCTTCCTT. The areas don’t code for amino acids, so they’re called non-coding multiple repeats
What is an allele
One of many forms of a gene
What is different about each allele
The order of bases, so they code for different versions of the same polypeptide
How many homologous pairs does each human cell have
23
What is different / the same in each homologous pair
Same size and genes, but can have different alleles
Where are alleles coding for the same characteristic in a homologous pair found
At the same fixed position (locus) on each chromosome in a homologous pair
