Introduction To Genetics Flashcards
What is DNA?
a chemical which carries genetic code
What is a gene?
a piece of DNA, or a location on a DNA
- DNA base pairs make up genes which make up
chromosomes
What do genes code for?
polypeptides
What does DNA stand for?
deoxyribonucleic acid
What is the shape of DNA
double helix (like a twisted ladder)
What does a dominant gene mean?
it is more common
What does a recessive gene mean?
it is less common
How was the shape of DNA discovered?
by using x-ray crystallography to discover the double helical shape of DNA
Who discovered the double helical shape of DNA?
James Watson and Francis Crick stole photograph 51 from Rosalind Franklin so they got credit for her discovery and won a Nobel Prize
What is a chromatid?
one of the two identical halves of a double-stranded chromosome
What is a centromere?
the linking structure of a pair of sister chromatids
How many pairs of chromosomes do humans have?
23 pairs
46 total
What is the exception to the rule of humans having 23 pairs of chromosomes
GAMETES have 23 chromosomes each (the egg has 23 and the sperm has 23) to make up a human which has 46 altogether
What makes up the ‘rungs’ of DNA?
bases/amino acids
What are the bonds for A, T, C, G
A + T = double bond
C + G = triple bond
What are the 2 amino acid pairs that make up DNA?
- Adenine + Thymine (A+T) - double bond, harder to break
- Cytosine + Guanine (C+G) - triple bond, easier to break
What is the way in which DNA strands run?
anti-parallel
What codes for an amino acid?
a triplet codon (multiple codes can code for one amino acid)
What makes up a free nucleotide?
- a base
- a pentose sugar
- a phosphate
What causes differences in DNA for different organisms?
differences in the number and arrangement of the amino acids in different organisms
How is the free nucleotide positioned on the one side of the DNA compared to the other?
it is upside down to the other side
Where are free nucleotides found?
floating around a cell
What is a karyotype?
an individual’s complete set of chromosomes in order of size usually
What is the male karyotype?
XY
What is the female karyotype?
XX
Which gender determines the sex of their baby and why?
Males determine the sex of the baby, as either the X sperm or the Y sperm fertilises the X egg.
- if the X sperm (which is a faster swimmer but lives for a shorter amount of time) fertilises the egg it will be female (XX)
- if the Y sperm (which is a slower swimmer but lives for a longer amount of time) fertilises the egg it will be male (XY)
What is the chance of your baby being male or female?
it is a 50/50 chance
