Heredity Flashcards
What is a chromosome?
A structure in which DNA (and proteins) are organised. Condensed DNA which is wrapped tightly in coils compacted in chromosomes to be stored in the nucleus.
What is a gene?
A sequence/section of DNA that codes for a protein
What is a karyotype?
A picture of all the types of chromosomes.
How many chromosome pairs are there in a human?
23 pairs
What is the last chromosome of a human?
A sex chromosome
Female chromosome?
xx
Male chromosome?
xy
What do people have if they have an extra chromosome?
Disorders
What things have chromosomes?
All living organisms have chromosomes
What do genes control?
Genes control the characteristics of living organisms
Genes are carried on what?
chromosomes
Chromosomes are in…
Chromosomes are in pairs, one from each parent meaning genes are pairs.
Genes are in…
Genes are in pairs
What do genes controlling the same characteristics occupy?
Genes controlling the same characteristics occupy identical positions (locus) on corresponding chromosomes.
When a dominant gene is written it is written with ….
A capital letter
e.g B
Define dominant gene
an allele which masks the effect of the recessive allele, gene
Define recessive gene
An allele which its effects are masked by a dominant allele, gene
Define allele
Different versions or alternatives of that gene
What is BB genotype? - example
Homozygous dominant
What is Bb genotype? - example
Heterozygous
What is bb genotype? - example
Homozygous recessive
Draw a punnet square
You should know if not sure look in book or online
What is a punnet square?
A tool which shows the two genotypes two individuals can produce when crossed
Define genotype
The combination of alleles or letters
Define phenotype
The observable or physiological characteristics of an organism
What is the last pair of chromosomes?
Sex chromosome
Genotype of type A blood
I^AI^A or I^Ai
Genotypes for type B blood
I^BI^B or I^Bi
genotypes for AB blood type
I^AI^B
genotype for type O blood
ii
Is cystic fibrosis recessive or dominant
recessive
is achondroplastic dwarfism dominant or recessive?
dominant
is albinism recessive or dominant?
recessive
is polydactyly dominant or recessive?
dominant
is sickle cell anaemia dominant or recessive?
recessive
Which of the following genes are alleles : A and A, A and B, B and C, B and b
A and A, B and b
what process separates homologous chromosomes?
Meiosis
describe genotype: bb
homologous recessive
What is the likely ratio of affected children born to parents of whom are heterozygous for cystic fibrosis?
1 affected: 3 normal
What phenotype corresponds to genotype: I^AI^O
Blood type A
Expected ratio of offspring from a black rabbit (Bb) and a white rabbit (bb)
50: 50
Which of the following is a ‘carrier’ genotype for a disease caused by a recessive gene?
nn, NN, Nn
Nn
If a child with cystic fibrosis have normal parents, what must the parents be?
‘Carriers’ - heterozygous for cystic fibrosis - Nn
