4. genetics, biodiversity and classification P1 Flashcards
What are the three components of nucleotides?
a pentose sugar, a phosphate group and an organic base
describe the structure of DNA [5]
- A polymer of nucleotides
- Each nucleotide is formed from deoxyribose, a phosphate group and an organic nitrogenous base.
- Phosphodiester bonds between nucleotides
- Double helix
- Hydrogen bonds between adenine, thymine and cytosine, guanine
Describe the role of DNA
Carries genetic information and determines are inherited characteristics
describe the structure of RNA
made up of a ribose sugar, a phosphate group and one of four organic bases. single stranded.
Uracil replaces thymine
describe the role of RNA
Transfers genetic information from DNA to ribosomes for protein synthesis
How is DNA in eukaryotic cells different from prokaryotic cells?
eukaryotic: found in nucleus,
pro: not
eukaryotic is associated with proteins/histones, whereas prokaryotic isn’t.
eukaryotic is linear, and prokaryotic is circular.
eukaryotic contains introns, and prokaryotic doesn’t
eukaryotic had no plasmids, but prokaryotic does.
name the fixed position occupied by a gene on a DNA molecule
locus
describe how a gene is a code for the production of a polypeptide. Do not include information about transcription or translation in your answer [3]
- the base/ nucleotide sequence.
- in triplets
- determines the sequence of amino acids/ primary structure in polypeptide.
define the term exon
the base/ nucleotide sequence coding for a polypeptide/ sequence of amino acids.
what is the genetic code?
the order of bases on DNA. consists of codons (triplets of bases that code for a particular amino acid)
Describe how phosphodiester bond is formed between two nucleotides within a DNA molecule [2]
- condensation reaction
- between phosphate and deoxyribose
- catalysed by DNA polymerase
identify features of the genetic code
- non-overlapping - each triplet is only read once
- degenerate - more than one triplet codes for the same amino acid
- universal - same bases and sequences used by all species
what is a gene?
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide.
what is an allele
different versions of the same gene found at the same locus on a chromosome.
what are introns? and where are they found?
regions of DNA that don’t code for anything, between exons within genes
define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome [2]
- DNA that doesn’t code for protein/ polypeptide
- positioned between genes
what is the genome?
the complete set of genes contained in the cells of an organism
what is the proteome?
the full range of different proteins that DNA is able to code for
suggest advantages of using mRNA rather than DNA for translation
single stranded and linear - ribosome moves along strand and tRNA binds to exposed bases
contains no introns
shorter - breaks down quickly so no excess polypeptide forms
describe the structure of tRNA
a single strand of nucleotides that is folded over in a clover leaf shape.
On one end is an anti-codon and on the other is an amino acid binding site
what is produced by transcription?
mRNA
give 3 ways in which the DNA in a chloroplast is different from the DNA in a nucleus [3]
- in chloroplasts, DNA isn’t associated with proteins, but nuclear DNA is
- the DNA in chloroplasts is circular, rather than the linear nuclear DNA
- introns are absent in chloroplasts but present in nuclear DNA
- DNA is shorter in chloroplasts
not all mutations in the nucleotide of a gene cause a change in the structure of a polypeptide. give 2 reasons why [2]
triplets code for the same amino acid, which occurs in introns/ non-coding sequence
what is a homologous pair of chromosomes?
two chromosomes that carry the same genes