Genetic disorders

Question 1

Define allele

Answer 1

Variant form of a gene in the same locus

Humans are diploid because they have two alleles at each genetic locus

Question 2

Define genotype

Answer 2

Pair of alleles represents a genotype of a specific genes

Broadly, the genotype refers to the genetic makeup of an organism

Question 3

Define homozygous

Answer 3

A genotype that features two identical alleles

Question 4

Define heterozygous

Answer 4

A genotype that features two different alleles

Question 5

Define phenotype

Answer 5

Composite of an organism’s observable characteristics or traits

Results from the expression or the interaction between an organism’s genotype and environmental factors

Question 6

Define dominant

Answer 6

Allele that will be manifested in the phenotype of a heterozygote

Question 7

Define recessive

Answer 7

Allele that won’t be manifested in the phenotype of a heterozygote, manigestation only results in homozygous individuals

Question 8

Define mutation

Answer 8

Permanent alteration of the nucleotide sequence in the genome

Question 9

Define wild type

Answer 9

An allele which is not mutated and codes the phenotype most common in a natural population

Question 10

Define SNP

Answer 10

Mutation carried by more that 1% of the population

Leads to variations in the amino acid sequence

Also occur in noncoding regions of DNA

If SNPs occur in a gene, the gene is described to have more than one allele

Does not significantly affect the phenotype, so is not selected for and therefore survives in the population

Question 11

Define mendelian disorder

Answer 11

Disorder controlled by a single locus in an inheritance pattern based on Mendel’s Law

Question 12

Define genetic susceptibility

Answer 12

Increased likelihood of developing a particular disease based on a person’s genetic makeup

Question 13

What information does DNA provide?

Answer 13

Information to understand how living organisms function

Study and treat disorders

Understand disease susceptibility

Study history and evolution

Make drugs

Understand and treat cancer

Question 14

What is a genetic disorder caused by?

Answer 14

One or more abnormalities in the genome

Question 15

TRUE or FALSE

All mutations are passed down

Answer 15

FALSE

Only if it occurs in the germline

Question 16

Example of an autosomal dominant condition

Answer 16

Huntington’s

Question 17

Example of an autosomal receissive condition

Answer 17

Cystic fibrosis

Question 18

Example of a X-linked disorder

Answer 18

Haemophilia A

Question 19

Example of a non disjunction condition

Answer 19

Trisomy 21

Question 20

Example of a condition caused by DNA deletion

Answer 20

Cri-du-chat

Question 21

What are the 4 types of genetic disorders?

Answer 21

Single gene

Chromosomal

Multifactorial

Somatic

Question 22

Types of chromosomal genetic disorders

Answer 22

Deletion

Duplication

Inversion

Translocation

Non disjunction

Question 23

Types of single gene genetic disorders

Answer 23

Autosomal dominant

Autosomal recessive

X-linked

Question 24

Pedigree of autosomal dominant conditions

Answer 24

Occurs in half of the offspring

Question 25

Pedigree of X-linked recessive

Answer 25

Men are affected Women are carriers For women to be affected, the mother must have both copies of the recessive allele

Question 26

Pedigree of a Y-linked dominant

Answer 26

Never occur in females Occur in all male descendent of an affected male

Question 27

Pedigree of X-linked dominant

Answer 27

If mother have the disorder Males and females have even chance of receiving conditions If father has the disorder Daughters will 100% get disorder None of the sons have disorder If both have the disorder - 100% of daughters will have disorder - 50% of sons will have disorder

Question 28

What is congenital afibrinogenemia?

Answer 28

Condition characterised by the lack of fibrinogen protein in the plasma Leads to increase in coagulation times

Question 29

What is fibrinogen?

Answer 29

Plasma hexameric glycoprotein

Question 30

Which cells secrete fibrinogen?

Answer 30

Secreted mainly by hepatic parenchymal cells

Question 31

What is the role of fibrinogen?

Answer 31

Plays an important role in haemostatic balance and support for platelet aggregation

Question 32

What mutation leads to congenital afibrinogenemia?

Answer 32

Mutation to one of the 3 fibrinogen genes FGA FGB FGG

Question 33

Describe the process behind polymerase chain reactions

Answer 33

Technique used to make copies of a specific DNA region in vitro Goal = make enough target DNA region so that it can be used

Question 34

How is Tag polymerase specialised for PCR?

Answer 34

Isolated from Thermus aquaticus bacteria It is very heat-stable Most active around 70C

Question 35

What is required for Taq polymerase to carry out its function?

Answer 35

Primer

Question 36

What are primers?

Answer 36

Specific sequences of DNA Bind via complementary base pairing

Question 37

What is gel electrophoresis?

Answer 37

Technique used to visualise PCR reactions Fragments of DNA are pulled through a gel matrix by an electric current which separates DNA fragments according to size Exploits the negative charge of DNA DNA fragments of the same length form a band on the gel which can be stained with a DNA-binding dye

Question 38

Describe the process behind Sanger sequencing

Answer 38

1. The DNA molecule is denatured 2. The solution with a single stranded DNA is added to DNA primers, DNA polymerase, four type of dNTPs and ddNTPs 3. ddNTPs bind (lack hydroxyl groups) and elongation is terminated 4. So if a ddNTP binds to the first complementary codon on a strand = reveals the first codon of the DNA

Question 39

How do ddNTPs terminate sequence elongation?

Answer 39

Lack hydroxyl groups Nucleotides without hydroxyl groups cannot create phosphodiester bonds with adjacent nucleotides

Question 40

How do ddNTPs tell which base it is bound to?

Answer 40

Colour coded

Question 41

What are types of point mutations?

Answer 41

Silent Nonsense Missense

Question 42

What are conservative point mutations?

Answer 42

Mutated protein's function is not too different from that of the wildtype Causes limited phenotypic expression

Question 43

What are non-conservative point mutations?

Answer 43

Do have a big effect on wild type since the protein expressed as a cause of the point mutation is very different from that of the wild type

Question 44

Mechanisms underlying point mutations

Answer 44

Substitution Insertion Deletion Inversion

Question 45

Describe the nomenclature for describing point mutations

Answer 45

g.1749T>G Gene 1749 T is replaced by G On amino acid 45 cysteine is replaced by phenylalanine