3.4.1.1 DNA, genes and chromosomes Flashcards
What is a gene?
A gene is a section of DNA that contains the coded information for making polypeptides and functional RNA.
What is the locus?
A locus is the position of a gene on a chromosome
What factors determine the nature and development of all organisms?
Genes and environmental factors
The genetic code uses 4 different DNA bases. What is the maximum number of different DNA triplets that can be made from these 4 bases?
4^3 = 64
What are some of the features of genetic code?
•It’s degenerative •It’s non-overlapping (each base only ready once) •It’s universal
Why is genetic code described as “degenerative”?
As one amino acid can be coded for by more than one triplet
Why is the genetic code described as being “universal”?
In all organisms the same triplet codes for the same amino acid;
What are exons?
Sequence that codes for amino acids.
What are introns?
Non-coding sequences (not ITNRested in them)
Why is the genetic code described as “non-overlapping”?
Each base in the sequence is only read once
Describe the DNA in prokaryotic cells
•DNA molecules are shorter •They form a circle •They aren’t associated with proteins (histones) •NO chromosomes
Describe the DNA in eukaryotic cells
•DNA molecules are longer •They form a line (linear) •They occur in association with proteins called HISTONES to form chromosomes
What is an allele?
Different form of a gene
Explain why the DNA base sequences of homologous chromosomes are almost the same.
Homologous chromosomes have the same genes At the same loci Different alleles (different forms of the same gene) usually only have a small difference in their base sequence
What name is given to the different forms of a gene?
Allele
what is this a picture of?
Nucleotide
Identify the blue circle in this nucleotide
phosphate
Identify the green shape in this nucleotide
deoxyribose (pentose sugar)
Indentify the pink rectangle in this nucelotide
organic base - either A T G or C
