Chromosones, DNA & Genes Flashcards
Sister chromatids
Two identical chromosomes held together by the centromere that make up a duplicated chromosome
Chromosomes
Thread-like structures
found in the nucleus of cells
made of DNA
Human cells contain how many chromosomes?
46 chromosomes which form 23 pairs - one inherited from the father & one from the mother
(Apart from sex cells which have only 23 chromosomes)
Sex chromosomes
2 sex chromosomes in every human cell
XY ➡ in male cell
XX ➡ in female cell
DNA
A large molecule that makes up chromosomes and contains genetic information
Nucleotide
A unit of DNA made up of a phosphate, a sugar (deoxyribose) and a base
Bases in DNA
A (adenine)
T (thymine)
G (guanine)
C ( cytosine)
DNA pairings
A with T
G with C
A Gene
(a distinct sequence of nucleotides forming part of a chromosome)
that has the code for making a protein
The genetic code
The rules (code) by which the information encoded in the DNA sequence is translated into the amino acid sequence
How do bases code?
In groups of 3 - 3 bases code for 1 amino acid
Gametes
- Sex cells - sperm & egg
- they are haploid cells; have only 23 chromosomes
Why do red blood cells have no chromosomes?
Because they have no nucleus, giving them more space to carry oxygen
Pairs of matching chromosomes
Homologous pairs
Diploid cells
Cells with chromosomes in pairs
