Genetics Flashcards
Who was responsible for the laws governing inheritance traits?
Gregor Mandel
What are Chromosomes?
Coiled up DNA. We have 23 pairs. One from Mum & one from Dad
What is a Gene?
A segment of a chromosome which contains the code of a specific trait. ie eye colour
What is an Allele?
Part of the Gene, contained within the Chromosome, that shows the characteristics of the particular trait. ie brown eye colour
What does Dominant mean?
Whenever this allele is present its characteristics will always be displayed within the trait.
What does Recessive mean?
The characteristic of this trait, unless paired with another recessive allele, will not be expressed.
What does Homozygous mean?
Two alleles that are the same i.e. RR (both dominant)
What does Heterozygous mean?
Two alleles that are different i.e. Rr (one dominant and one recessive)
What is genotype?
The outcome or parents in letter i.e. RR, Rr or rr
What is Phenotype?
The displayed characteristics in words i.e Brown Eyes, Blue Eyes
What is Monohybrid crosses?
Crosses involving a single trait
What are Dihybrid Crosses?
Crosses involving two traits
What are the 3 different types of Dominance?
Complete Dominance Incomplete Dominance Co-Dominant
What is complete Dominance?
The dominant allele completely masks the effect of the recessive allele in heterozygous pairs.
What is Co-Dominance?
Co-dominance occurs when the contributions of both alleles are visible in the phenotype. For example Red and white flower makes a stripy red and white flower.
What is Incomplete dominance?
Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes. For example pink flowers.
What is an Autosome?
A non sex linked Chromosome. Therefore chromosomes 1 - 22
What are Autosomal Disorders?
Disorders that are located on Chromosome 1 - 22
What is Autosomal Recessive Disorders?
A disorder that must receive a disorder allele from mum and one from dad to be present. Don’t forget mum & Dad can be carries.
What is Autosomal Dominant Disorders?
Only needs to receive the disorder allele from one parent to present with the condition.
What is Sex-Linked Inheritance?
Traits that are carried on Chromosome 23.
Why are most sex linked traits carried on the X chromosome?
Because the Y chromosome is smaller.
What are the quick ways to tell if the condition is recessive of dominant?
The odds of children having the disease i.e 1 in 4 recessive or 1 in 2 dominant. If the disease is present in mum or dad = dominant. If both mum and dad are carriers disease is recessive.
When doing blood group squares, how is the genotypes written? What sort of dominance is blood group?
IA IA or IA i = A group
IB IB or i = B Group
IA IB = AB Group
ii = O Group
Co-Dominant
With Dihybrid Crosses what is the ratio for 2nd Generation crosses normally?
9:3:3:1
When drawning a Dihybrid punnit square what do you NEED to remember to put in RATHER than parents?
To put in the possibilities from the parents rather than the parents.
i.e RrYy = Possible genotypes RY, Ry, rY, ry - Dont put in RrYy
Is huntingtons disease sex linked or not and is is Dominant or recessive?
It is autosomal. You can inherit Huntington’s disorder if one or both of your parents carry the faulty allele, because it is a dominant allele.
IS Cystic Fibrosis caused by a recessive or Dominant Trait?
Cystic fibrosis (CF) is caused by a recessive allele and is not sex linked and can by passed by mother or father.
Name some Sex linked diseases?
Haemophillia
Colour blindness
Bauldness
