Genetics

Question 1

What is genetics ?

Answer 1

-The study of heredity in general and genes in particular

Question 2

What is heredity ?

Answer 2

-The passing of traits from parent to offspring

Question 3

Why did Mendel use pea plants?

Answer 3

-Easy to cultivate, available in many varieties, produce large number of offspring, strict control over mating/breeding

Question 4

What is true breeding?

Answer 4

-When plants self-pollinate and all their offspring are of the same variety

Question 5

What is hybridisation?

Answer 5

-Mating or crossing of two varieties

Question 6

What is a monohybrid cross?

Answer 6

-A cross between two parents that breed true for different versions of a single trait

Question 7

What did Mendel do?

Answer 7

-Cross pollinated two true breeding varieties studying one trait at a time, then recorded the inheritance of the chosen trait in the next generation, then allowed the F1 plants to self fertilise and observed F2

Question 8

What is a homozygous gene?

Answer 8

-Gene possessing two identical alleles

Question 9

What is a heterozygous gene ?

Answer 9

-Gene possessing two different alleles

Question 10

What does Mendel’s law of independent assortment state?

Answer 10

-During gamete formation, different pairs of alleles segregate independently of one another

Question 11

What is a genetic disease?

Answer 11

-A disease that is caused by an abnormality in an individuals DNA

Question 12

What are the 4 types of genetic disorders?

Answer 12

-Single gene defects, chromosome abnormalities, multifactorial disorders, cancer

Question 13

What is cancer?

Answer 13

-Progressive accumulation of mutations in different genes and different chromosomes abnormalities, usually in somatic cells

Question 14

What are single gene disorders?

Answer 14

-Caused by changes or mutations that occur in the DNA sequence of a single gene, producing either an altered protein or no protein at all

Question 15

What can single gene disorders lead to?

Answer 15

-Gain of function loss of function which result in a protein alteration or deficiency responsible for disease symptoms

Question 16

What are the different mechanisms of inheritance?

Answer 16

-Autosomal dominant, autosomal recessive and X-linked recessive or dominant

Question 17

What is an autosomal dominant mechanism?

Answer 17

-A single mutated allele is sufficient to cause the disease (heterozygous)

Question 18

What is an autosomal recessive mechanism?

Answer 18

-Where both mutated alleles must be inherited to be affective (homozygous)

Question 19

What is x-linked recessive or dominant?

Answer 19

-Mutated gene is present on the X chromosome

Question 20

How do missense mutations alter coding in genes ?

Answer 20

-Base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid

Question 21

How do nonsense mutations alter coding in genes?

Answer 21

-Base changes that convert an amino acid codon to a stop codon resulting in premature termination of translation

Question 22

What are silent mutations?

Answer 22

-Do not cause any change in an amino acid

Question 23

What are frameshift mutations?

Answer 23

-Result from the insertion or deletion of one or more bases causing the alteration of the reading frame of the gene and a different set of codons leading to an altered ….

Question 24

What can chromosome abnormalities be classified into ?

Answer 24

-Numerical and structural

Question 25

What are numerical abnormalities ?

Answer 25

-When an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes in a pair (trisomy)

Question 26

What are structural abnormalities ?

Answer 26

-When the chromosomes structure is altered

Question 27

What is euploid?

Answer 27

-Normal number of chromosomes

Question 28

How is aneuploidy caused?

Answer 28

-Nondisjunction events in meiosis

Question 29

What is mosaicism?

Answer 29

-The presence of two or more cell lines with different chromosome compositions in an individual

Question 30

What can changes in chromosome structure cause?

Answer 30

-Deletions -Duplications -Inversions -Translocations

Question 31

What is a deletion ?

Answer 31

-Loss of a chromosome segment

Question 32

What is a duplication?

Answer 32

-Repeats of a segment

Question 33

What is inversion?

Answer 33

-Where a portion of the chromosomes has broken off, turned upside down and re-attached so genes occur in reverse order

Question 34

What is a translocation mutation?

Answer 34

-A portion of one chromosome is transferred to another, can be reciprocal

Question 35

What are multifactorial disorders?

Answer 35

-Diseases that show familiar clustering but do not conform to any recognised pattern of single gene inheritance

Question 36

How are multifactorial disorders determined?

Answer 36

-The additive effects of many genes at different chromosomes together with the effect of environmental factors

Question 37

What is an example of multi factor disorders?

Answer 37

-Diabetes, hypertension, obesity

Question 38

What are the fundamental properties of cancer cells?

Answer 38

-Unregulated cell proliferation and metastatic spread

Question 39

How does activation of oncogenes contribute to cancer?

Answer 39

-Proto-oncogenes become switched on and become hyperactive oncogenes

Question 40

What do promo-oncogenes do?

Answer 40

-Stimulate cell division in response to specific signals

Question 41

How does inactivating tumour suppressor genes contribute to cancer?

Answer 41

-In normal cells they block cell division at checkpoints of they are not ready and initiate apoptosis but in cancer cells this is permanently switched off

Question 42

What happens in cancer cells that causes uncontrolled cell growth?

Answer 42

-Unable to stop cell cycle and enter G0 even with DNA damage and programmed cell death pathways are also inhibited

Question 43

What are genetic polymorphisms ?

Answer 43

-Two or more existing different forms of DNA sequences in a certain gene within a population (at least 1%)

Question 44

Where are polymorphisms found?

Answer 44

-Outside genes in DNA sequence that does not code for proteins

Question 45

What are the functions of polymorphisms ?

Answer 45

-Determine the diversity of individuals and sometimes have a role in drug response, forensics or could represent risk factors for multi factor disease

Question 46

What is gene expression?

Answer 46

-When a gene is turned on so protein synthesis occurs

Question 47

What is epigenetic?

Answer 47

-The process of turning genes on or off

Question 48

What does a histone and acetyl do?

Answer 48

-Acetylation-lowers attraction so DNA unwinds so open access to DNA strand is present

Question 49

What happens to DNA when deacetylation occurs ?

Answer 49

-DNA is lock tight

Question 50

What happens when there is one methyl group on a histone?

Answer 50

-Decreases attraction so unwinds DNA so DNA replication can take place

Question 51

What happens if there is two or more methyl groups on a histone?

Answer 51

-DNA will repress and be lock tight so gene expression can not occur

Question 52

What can adenosine be changed for during RNA editing?

Answer 52

-Inosine

Question 53

What can cytosine be changed for during RNA editing?

Answer 53

-Uracil

Question 54

How is a gene turned on?

Answer 54

-Enhancer is activated by the activator and bend over to the transcription factor