DNA, Genes and Chromosomes Flashcards
(25 cards)
What are some characteristics of DNA molecules in prokaryotic cells?
- Shorter molecules
- Circular
- Not associated with proteins (‘naked’)
What are some characteristics of DNA molecules in mitochondria and chloroplasts?
Same as that if prokaryotic cells:
- Shorter molecules
- Circular
- Not associated with proteins (‘naked’).
What are some characteristics of DNA molecules in eukaryotic cells?
- Very long molecules
- Linear
- Associated with histone proteins
How does a DNA molecule and its associated proteins form a chromosome?
- DNA double helix wraps around the histone proteins forming a structure called a nucleosome.
- The DNA histone complex is coiled further and then looped to form the chromosome structure.
- In the visible chromosome the DNA and protein is described as condensed chromatin.
What happens to chromosomes in prophase?
They become visible in the nucleus.
How many chromatids are each chromosome made of?
2
Where are chromosomes inherited from?
One from the mother and one from the father.
What does diploid mean?
Two copies of each chromosome
What does haploid mean?
One copy of each chromosome
What is a gene?
A sequence of DNA bases that contains the coded information for making polypeptides and functional RNA.
Where are specific genes located for all members of a species?
The same position (locus) on the same chromosome.
What is the expression of a gene often associated with?
A trait / phenotype
What is an allele?
One of a number of different forms of a gene.
What causes different forms of a gene (alleles)?
- They each have a slightly different sequence and / or number of bases.
- These different variation of a gene arise by mutation.
What are laris of matching chromosomes called?
Homologous pairs
What is the same / different in the two chromosomes that make a homologous pair?
- They are both the same size
- The both have the same genes
- Alleles coding for the same characteristic will be found at the same fixed position (locus)
… - They could have different alleles
What is a genome?
The complete set of genes (and DNA) in a cell or organism, including the mitochondria and chloroplasts.
What is a proteome?
The full range of proteins produced by the cell / organism.
What is a DNA triplet?
A sequence of three DNA bases that codes for a specific amino acid.
What are the features of the genetic code?
- Universal
- Non-overlapping
- Degenerate
What does it mean to say the genetic code is universal?
In all organisms, the same triplet codes for the same amino acid.
What does it mean to say the genetic code is non-overlapping?
Each base is only part of one triplet.
What does it mean to say the genetic code is degenerate?
More than one triplet can code for each amino acid.
What is the codon that starts all protein synthesis?
AUG (methionine)
