G1- hitch hikers guide to human genome

Question 1

what is the replication of the human genome?

Answer 1

cell cycle and mitosis meisosis

Question 2

what is the organisation of genes?

Answer 2

Promotors, start codons, introns and exons

Question 3

What turns a gene into a protein?

Answer 3

Transcription, splicing and translation

post-translational modification and transport

Question 4

what provides variation in the human genome?

Answer 4

Polymorphisms

Mutations

Question 5

what contributes to disease?

Answer 5

• genes

- environment

Question 6

what do genes control?

Answer 6

control predisposition to ALL common disease – eg. Caries, oral cancer

Question 7

what is genetics being increasingly used for?

Answer 7

determine treatment

Question 8

Describe the DNA structure.

Answer 8

• Strands of DNA pair up in an antiparallel fashion

• DNA is replicated and read
always in the 5’ –> 3’ direction
-bases are A,T, C, G

Question 9

How is information in DNA held?

Answer 9

held in the sequence of the bases which are held on a sugar/phosphate backbone

Question 10

what does the DNSA strand associate with?

Answer 10

associates with proteins (including histones) and is wound into a structure called a chomosome

Question 11

What are the stages of the cell cycle?

Answer 11

M-mitosis
G1- gap 1
Go-resting
S-synthesis (DNA)
G2-gap 2

Question 12

Describe DNA damage and repair.

Answer 12

• DNA strand breaks
• Chemical crosslinking
• mismatched base

Question 13

when does DNA replication happen?

Answer 13

during S phase

Question 14

Describe key facts of DNA damage.

Answer 14

• DNA can be damaged during replication
• Repair mechanisms exist
• Defects in these repair mechanisms cause disease

Question 15

What does mitosis produce from one diploid parent cell?

Answer 15

Two identical diploid daughter cells

Question 16

what does meiosis produce from one diploid parent cell?

Answer 16

4 Haploid daughter cells

one of each chromosome to each cell

Question 17

Describe crossing over at meiosis.

Answer 17

genes segregate independently, even if on the same chromosome

Question 18

what does meiosis occur?

Answer 18

Occurs in gamete formation

Question 19

what is different about RNA compared to DNA?

Answer 19

• Single stranded
• Ribose in backbone not deoxyribose
• Uracil (U) is used instead of Thymine (T)

Question 20

what determines the amount of protein produced?

Answer 20

• Rate of transcription (manufacture of Pre-mRNA)
• Rate of splicing to mRNA
• Half life of mRNA
• Rate of processing of polypeptide

Question 21

Describe the change from DNA to protein.

Answer 21

-DNA is transcribed to pre mRNA
-Pre mRNA is spliced to mRNA
-mRNA is translated to protein
3 bases encode 1 amino acid or a stop
-Protein is modified and moved round the cell

Question 22

what causes sequence variations within a gene?

Answer 22

• Changes in the promotor sequence
• Changes in the exon sequence
• Ones that change an amino acid
• Sequence changes that do not

Question 23

what causes sequence changes in the DNA between genes?

Answer 23

• Single Nucleotide polymorphisms (SNPs)

- Larger deletions or duplications

Question 24

what are polymorphisms?

Answer 24

-Any variation in the human genome that has a population frequency of greater than 1%

or

-Any variation in the human genome that does not cause a disease in its own right. It may however, predispose to a common disease

Question 25

what are mutations?

Answer 25

-A gene change that causes a genetic disorder. (a disease causing mutation) Or -Any heritable change in the human genome

Question 26

why do variants of genome all segregate independently of each other?

Answer 26

because of crossing over at meiosis

Question 27

what Is a genetic disease?

Answer 27

One caused by a change in the genes

Question 28

Name some of these changes in gene?

Answer 28

``` Extra piece of chromosome Missing piece of chromosome Change in gene sequence Insertion or deletion of a few bases Change of a single base where it matters ```

Question 29

what is the purpose of genome knowledge?

Answer 29

To know what a DNA test result means and use it for patient management

Question 30

what does phenotype equal?

Answer 30

genotype + environment

Question 31

what does all disease equal?

Answer 31

genes + environment

Question 32

what is penetrance?

Answer 32

The likelihood of having a disease if you have a gene mutation

Question 33

what does 100% penetrance mean?

Answer 33

you will always get the disease if you have the mutation

Question 34

what are mendelian disorders?

Answer 34

-Diseases that segregate in families in the manner predicted by Mendel’s Laws -Essentially a disease that is predominantly caused by a change in a single gene (High penetrance)

Question 35

what allows us to select one small pice of the human genome from a patient and amplify it?

Answer 35

Polymerase Chain Reaction (PCR) -make lots of copies of one short stretch of the genome

Question 36

what results from promotor mutation?

Answer 36

- No, or reduced transcription | - No, or reduced protein

Question 37

what results from splice consensus altered?

Answer 37

- mRNA decay | - Abnormal or absent protein

Question 38

what results from a base change makes a new stop?

Answer 38

- mRNA decay] | - short or absent protein

Question 39

what results from base change that alters amino acid sequence?

Answer 39

different or non-functioning protein

Question 40

Name the types of mutation in DNA sequences.

Answer 40

- wild type - stop - missense - insertion - deletion (out of frame) - deletion (in frame) - triplet expansion

Question 41

Can different mutations in the same gene cause the same disease?

Answer 41

Yes

Question 42

what effect does different mutations have?

Answer 42

have different effects on the protein produced and these can be predicted

Question 43

what is non-mendelian inheritance?

Answer 43

Everything else including common “multifactorial” diseases

Question 44

why sometimes is a child affected but neither parent seems to be affected?

Answer 44

- New mutation occurs as genes transmitted to child - Parent doesn’t show clinical features but carries mutation (non-penetrance) - Parent carries mutation but has very mild disease (variable expressivity

Question 45

what different outcomes can gene mutations have?

Answer 45

-Mutations can affect the same gene in different ways, Leading to different disease processes but -Mutations in different genes can also cause the same Disease

Question 46

what is used to find out diagnosis?

Answer 46

- clinical history - family history - clinical examinations - genetic tests

Question 47

what can we do with diagnosis?

Answer 47

- recurrence risk - treatment - prognosis - genetic tests