Genetics Flashcards
What chemical are chromosomes and genes made from?
DNA
Put the following biological structures in size order starting with the largest: cell, chromosome, DNA, nucleus, gene
cell → nucleus → chromosome → gene → DNA
The allele for brown eyes (B) is dominant over the allele for blue eyes (b).
What colour eyes would these people have:
BB
Bb
bb
The people with BB and Bb would have brown eyes because a dominant allele is always expressed (even if only 1 copy is present).
The person with bb would have blue eyes because a recessive allele is only expressed when 2 copies are present (no dominant allele).
Which one of these people is heterozygous:
BB
Bb
bb
Bb because the 2 alleles are different.
Which of these people are homozygous:
BB
Bb
bb
BB and bb because the 2 alleles are the same.
The allele for brown eyes (B) is dominant over the allele for blue eyes (b).
A woman has blue eyes.
What are the woman’s alleles?
bb because the allele for blue eyes is recessive and a recessive allele is only expressed when 2 copies are present.
How many chromosomes does an ordinary human body cell contain?
46 / 23 pairs
What is a gene?
A small section of DNA on a chromosome.
Codes for a specific protein.
Describe the structure of DNA
Made of 2 strands which twist around each other to form a double helix
What are chromosomes?
Long pieces of DNA.
Found in the nucleus of cells.
Carry many genes.
Normally found in pairs (one from each parent).
What are alleles?
Different versions of the same gene i.e. you have a gene for eye colour but there are versions which give blue eyes and versions which give brown eyes.
What is the difference between a dominant allele and a recessive allele?
A dominant allele is always expressed even if only one copy is present.
A recessive allele is only expressed if 2 copies are present (no dominant allele).
Define homozygous.
2 alleles for a particular gene are the same e.g. BB or bb.
Define heterozygous.
2 alleles for a particular gene are different e.g. Bb.
Define genotype.
The genes / alleles a living organism has.
Define phenotype.
A living organisms characteristics (physical features).
Give the combination of sex chromosomes present in a male and a female.
Male XY
Female XX
Draw a genetic diagram to show sex inheritance.
Chance of male offspring = 50 %
Chance of female offspring = 50 %
What is DNA?
A chemical that holds the genetic material (the code for making proteins).
Contained in structures called chromosomes.
Give characteristics which are the result of the genes a living organism has inherited from its parents.
Characteristics which you are born with and can’t change.
Blood group
Eye Colour
Earlobe shape
Give characteristics which are the result of the conditions in which an organism has developed (environmental).
Scar
Language
Accent
What is a mutation?
A change in the DNA.
Give characteristics which are the result of both the genes an organism has inherited from its parents and the conditions in which the organism has developed (environmental).
Skin colour
Weight
Height
What is cell division?
Parent cell divides to produce two genetically identical cells.
Why is cell division important?
Growth
Repair
What has to happen before a cell divides?
DNA replicates to form 2 copies of each chromosome.
A human cell cells divides to produce two genetically identical cells.
How many chromosomes are there in each new cell?
46 or 23 pairs
The allele for brown eyes (B) is dominant over the allele for blue eyes (b).
A man with alleles Bb and woman with the alleles Bb plan to have a child.
What is the chance the child will have:
a) brown eyes
b) blue eyes
a) BB, Bb and Bb all have brown eyes so a 75 % chance of the child having brown eyes.
b) bb has blue eyes so a 25 % chance of the child having blue eyes.
Polydactyl is an inherited disorder.
The allele for having polydactyl is dominant (D).
The allele for not having polydactyl is recessive (d).
A man with the alleles DD and woman with the alleles dd plan to have a child.
What is the chance the child will have polydactyl?
Dd has the disease so a 100 % chance of the child having polydactyl.
