59 WJEC Biology AS Level - Study And Revision Guide - Neil Roberts (1.6 The Cell Cycle And Cell Division) Flashcards
What do chromosomes consist of ?
Chromosomes consist of
- DNA
- A protein called histone
Are chromosomes visible all the time?
No.
When are chromosomes visible?
They are only visible after they condense at the onset of cell division.
How does the chromosome exist following DNA replication?
Following DNA replication, a chromosome exists as:
Two identical ‘sister’ chromatids joined by the centromere.
What is the genetic similarity between sister chromatids?
Sister chromatids are genetically identical.
What does each chromosome contain?
Each chromosome contains genes that code for specific polypeptides.
Do all species have the same number of chromosomes?
No.
Different species have different numbers of chromosomes.
How many chromosomes do humans have?
How many chromosomes do potatoes have?
Humans have 46 chromosomes
Potato has 48 chromsomes.
How many pairs of chromosomes do humans have?
Where do they come from?
In humans, chromosomes come in 23 pairs.
In each pair, one chromosome comes from each parent.
What are homologous chromosomes?
Each pair of chromosomes contain two homologous chromosomes.
They contain the same genes but they may be different versions or alleles.
What do you mean when you say diploid?
Where an organism is said to have two complete sets of chromosomes this is called diploid
What is the diploid number in humans?
In humans the diploid number (2n) is 46.
How many sets of chromosomes does a potato have?
What is this called?
The potato has four complete sets of chromosomes.
This type of polyploidy is referred to as tetraploid (4n).
Where are haploid number of chromosomes seen?
Haploid (n) numbers are found in
- human gametes.
- mosses
- male worker bees.
Gene (Key-Term)
A base sequence of DNA that codes for the amino acid sequence of a polypeptide.
Each gene occupies a fixed position on the chromosome called the locus.
Draw the structure of a chromosome.
