L11- Genotype, Phenotype + Inheritance Flashcards
A) What is inheritance?
b) Define allele
C) Define genotype
D) Define phenotype
A) How characteristics are passed on from one generation to the next
B) Version of a gene
C) genetic combination of 2 alleles
D) Physical expression of a gene (determined by genotype and environment)
Each human has 25,000 genes. What makes up each gene?
- each individual has 2 copies (alleles) of each gene-> one allele inherited from father (paternal) and one inherited from mother (maternal)
- some alleles may not be expressed but can be passed onto next generation
Define:
A) homozygous
B) Heterozygous
C) Hemizygous
A) two alleles of a gene are the same (individual is a homozygote)
B) two alleles of a gene are different (individual is a heterozygote)
C) only one allele of a gene on the X chromosome (males only)
Compare dominant vs recessive inheritance
Dominant:
- dominant trait: only one allele is required for it to be expressed
- dominant allele will mask a recessive allele
- denoted by capital letter: A
- e.g. AA or Aa will have dominant trait
Recessive:
- when a trait is recessive: 2 copies of a recessive allele needed to express trait
- denoted by lower case letter e.g. a
- only aa genotype will express (homozygous recessive)
What is:
A) dominant gene
B) recessive gene
A) a gene whose trait is always expressed when present
B) a gene whose trait may not be expressed if it is masked by the presence of a dominant gene
What is co-dominance?
When 2 versions or alleles of the same gene are present and both are expressed. Neither are dominant over the other.
Outline how blood groups show co-dominance?
- Human isoglutamin gene codes fro glycoproteins on surface of RBC
- Gene: I
- 3 different alleles: A,B or O (I^A, I^B or I^O)
- Allele A: dominant over allele o
- Allele B: dominant over allele o
- Neither A or B dominant over each other: co-dominant
- 4 phenotypes (genotype in brackets): Blood group A (I^A I^A, I^A I^O), Blood group B (I^B I^B, I^B I^O), Blood group AB (I^A I^B) and Blood group O (I^O I^O)
A) What is an autosomal recessive pattern?
B) Example of disease
C) Characteristics
D) What is the chance of 2 carrier parents having an affected offspring?
A) occurs non-sex chromosome and 2 alleles of the gene needs to be present for the offspring to be affected
B) cystic fibrosis
C) - males and females are affected equally
- can skip generations
- heterozygotes are unaffected just carriers
- Both parents of affected individuals are heterozygous
D) 25%
A) What is autosomal dominant inheritance?
B) Example
C) Characteristic
D) what is the chance of affected individuals having affected offspring?
A) gene on non sex chromosomes and only one allele needs to. Be present for an individual to be affected i.e. homozygous and heterozygous individuals
B) Huntington’s disease
C) - male and females equally affected
- cannot skip a generation
- all affected individuals must have at least one affected parent
- disease is rarely found in homozygous state as not viable for life
D) 50 percent
A) What is X-linked inheritance?
B) Why is expression in females and males not the same?
C) Where do males get their sex chromosomes from and where do females get theirs from?
A) the genes causing the trait or disorder is located on the X chromosome?
B) Males are XY and females are XX
C) Males get their X chromosome from mum and their Y chromosome form Dad
- females get one X chromosome from their mum and one X chromosome from their dad
A) What is X-linked recessive inheritance?
B) Example
C) Is this kind of disease more common in females or males and why?
D) If you have an affected male what does their mother have to be?
E) If you have an affected female what will their mother and father be?
A) A mode of inheritance in which the mutation in a gene on the X chromosome causes the phenotype to be expressed in hemizygous males and homozygous females
B) Haemophilia A
C) More common in males because males get X chromosomes from their mum and the son will always get it if their mum has it and has a 50 percent change of getting it if their mum is a carrier
D) At least heterozygous
E) An affected father and carrier mother or an affected father and an affected mother
A disease is X-linked recessive. What is the chance of the son being affected in the following scenarios:
A) Mother is heterozygous carrier
B) Mother is homozygous
A) 50% (remember it doesn’t matter what father is as it is X linked!)
B) 100%
A) What is X-linked dominant? B) Example? C) What is the chance of the following individuals having affected children (include whether it will be male or females) I) Affected father only II) Carrier mum and unaffected dad IIi) Both parents carriers
A) The dominant gene carried on the x-chromosome, only one copy of the allele sufficient to cause the disease (affects hemizygous males and homozygous females)
B) Rickets (vitamin d deficiency) or Retts syndrome
C) i) 100% daughters and 0% sons as sons don’t receive an X from their dad
II) 50% of children (either sex)
IIi) 100% females affected and 50% chance males affected
A) What are Y-linked disorders?
B) Why are they so rare
C) give an example?
A) those linked to mutant alleles on the Y chromosome (which is unique to males and hence can only be passed on from male to male)
B) Y Chromosome is small and few genes
C) Infertility
A) What is mitochondrial inheritance?
B) What is mitochondrial dna and how is it different to normal DNA?
C) What organs/tissues would you expect to be affected with people who have mitochondrial disease and why?
A) The inheritance of a trait encoded in the mitochondrial genome
B) Each mitochodnrion has a chromosome made up of mtDNA, it is different as it is round and small, it contains 37 genes which are essential for the normal function of the mitochondria
C) Those tissues with the highest energy demand as the main function of the mitochondria is to produce ATP
