Chapter 3- Genetics- Theoretical Genetics Flashcards
Define phenotype
Characteristics of traits of an organisms
Eg: five fingers, colour blindness and type O blood
Define genotype
Symbolic representation of a pair of alleles possessed by an organism
eg: Bb GG tt
Define dominant allele
Always expressed when its present it cannot be masked by a normal allele
Define recessive allele
Can be masked by another allele- only expressed when 2 copies are present
Define co dominant allele
Pairs of alleles that both have affect on the phenotype when present on a heterozygous
Define locus
Particular position on homologous chromosomes of a gene. Each gene is found on a specific pair of chromosomes
Define homozygous
Having 2 identical alleles of a gene
Eg: AA
Define heterozygous
Having 2 different alleles of a gene
Eg: Aa
Define carrier
An individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this alleles
Define test cross
Testing a suspected heterozygous by crosses it with a homozygous recessive
Do a diagram of a punnet grid
Martha.
What is an example of genes that have more that 2 alleles?
ABO blood group system in humans
How does the ABO work as 3 alleles?
Share co-dominance (can be expressed equally in phenotype) and share incomplete dominance (neither fully expressed phenotype=blending)
What do ABO blood types demonstrate ?
A dominance order (allele A > allele B > allele C)
What are the four possible phenotype types for ABO blood groups?
A, B, AB and O
How to ABO create these 4 blood types?
There are 3 alleles of the gene and these alleles can produce 6 different genotypes
What is the gene for ABO blood type represented as?
Letter I
What is the allele for type A blood group?
I^A
What is the allele for type B blood group?
I ^ B
What is the allele for type O
ii
Crossing over of the ABO gives how many possibilities?
6
What does I^A I^A or I^A i give?
Gives phenotype blood group A
What does I^B I^B or I^B i give?
Blood group B
What does I^A I^B give?
Type AB
What does ii give in blood groups?
Blood group O
Antigen A has what type of antibodies?
And what type of blood can’t it have/have?
Anti-B antibodies and can’t have B or AB blood but can have O or A blood
Antigen B what type of antibodies does it have? And what type of blood can it have/can’t have
Has anti-A antibodies and can’t have A or AB blood but can have B or O blood
What type of antibodies does antigen AB have? And type of blood can it have/can’t have
Doesn’t have any antibodies but can have any blood type- it is the universal recipient
What types of antibodies has A and B?and what types of blood can it only have?
Has both A and B antibodies and can only have O blood- is the universal donor
How many pairs of chromosomes do humans have?
23
What are the first 22 chromosomes known as?
Autosomes- each chromosome pairs possess the same genes and structural features
What is the 23rd chromosome responsible for and known as?
Heterosomes (sex chromosome) and determines gender
What is the father always responsible for?
Determining gender
If male sperm contains X chromosome the embryo will defiently be?
A girl
There is always a 50\50% chance on what? Also draw the grid to prove it
That is will be a boy or a girl
A Y chromate is different in size to an X chromosome how?
It is much smaller and only contains a few genes- has fewer loci
On males where are the majority of alleles present? And what does this impact?
On the X chromosome and have no alleles to pair with on the smaller Y chromosome
Define sex linkage
Any genetic trait whose allele has its locus on the X chromosome is sex linked
What are colour blindness and haemophilia both examples of?
X-linked recessive condiitions
Where is the gene loci found for colour blindness/haemophilia on the X chromosome?
On the non-homologous region of the X chromosome (not present in Y chromosome)
Why can’t males carry the gene for colour blind embeds and haemophilia?
As males only have one allele for this gene they cannot carry it for the condition
As males can’t carry the gene for haemophilia and colour blindness what does this mean they have a higher frequency of?
Higher frequency of being recessive and expressing trait
Where do males inherit X linked recessive conditions from?
The mother
Where do females inherit sex linked conditions from?
Females only inherit an X linked condition if they receive a recessive gene from both parents
What is the genotype for affect and unaffected haemophilia?
X^H= unaffected X^h=affected
What is the genotype for affected and unaffected colour blindness
X^A=unaffected X^a=affected
Draw a punnet grid to show how males and females inherit colour blindness and haemophilia
Fucking do it
Why can females be homozygous or heterozygous with respect to sex linked genes?
As human females have 2 X chromosomes (and therefore 2 alleles for any give X-linked gene) they can be either homozygous or heterozygous
Why can men only be hemizygous?
Only have 1 X chromosome (therefore only 1 allele)
Why can females be carriers for X linked recessive conditions?
Because they have 2 chromosomes– males X Y can’t
So why does a male have a greater chance of getting a sex linked condition?
Cuz a male only inherits an X chromosome from his mother not his father.
Draw a punnet grid to show autosomal dominance/recessive
Jf kana
Draw a punnet grid to show co dominance
Draw a punnet grid to show x-linked recessive
On a pedigree chart what represents an unaffected female and an affected female
Unaffected- white circle
Affected- black circle
On a pedigree chart what represents an Unaffected male and an affected male?
Affected= black square Unaffected= white square
All affected individuals must have at what on a pedigree chart?
At least one affected parent
If 2 parents are unaffected on a pedigree chart what are the offspring?
All must be unaffected
If 2 parents are affected on a pedigree chart what are the offspring?
May have offspring who are affected if parents are heterozygous
Draw a diagram of a pedigree chart with a dominant allele as parents
Baka
Draw a pedigree chart with a recessive allele as parents
Kahslanipasbbshdsk
