What is a genome?

Question 1

Genomics

Answer 1

Study of an organism’s complete set of genetic info. ‘genome’ = the complete genetic information of an organism. Genome includes both genes and non-coding DNA

Question 2

Genetics

Answer 2

The study of heredity. The study of function and composition of single genes. Gene - specific sequence of DNA which code for a functional molecule.

Question 3

Gene is

Answer 3

difficult to define

Question 4

How many genes in the human genome?

Answer 4

20,000-25,000 genes

Question 5

What do genes do?

Answer 5

Basic functional unit for heredity. Codes for products that may become proteins, RNAs or alternatively spliced versions of either. Can include enhancers and promoters

Question 6

How big are genes?

Answer 6

Highly variable, human genes range from 0.9 - 2,400kb

Question 7

What is a structure of a gene?

Answer 7

Enhancers and promoters potentially, start codon, ORF (exons and introns), Stop codon, alternative splice sites potentially included

Question 8

How variable is the structure of our genes?

Answer 8

Must start with start codon. Must end with stop codon. at least a single exon. Exerything else can be variable

Question 9

Types of variation in our genes?

Answer 9

Inversions and balanced translocations or genomic imbalances (insertions and deletions), = copy number variants (CNVs)

Question 10

Gene organisation

Answer 10

genes are of various different sizes, range from 1 exon to 79 exons (DMD)

Question 11

Genes can also code for

Answer 11

protein

Question 12

Some genes not involved in

Answer 12

protein coding, they code for RNA only

Question 13

There’s an entire level of the

Answer 13

transcriptome; could be over 100,000 transcripts which generate more than a million different proteins which makes up the proteome. This comes from a relatively small number of genes around 20-25,000 genes

Question 14

Initially how many genes did scientists think existed?

Answer 14

50,000 but actually there are less than originally expected. This doesn’t mean that there’s’ not diversity in a large numbers of different proteins that are produced

Question 15

Haploid human genome sequence

Answer 15

Non-coding sequence elements, exons, introns, RNA coding and regulatory sequences and genes

Question 16

• Non-coding sequence elements =

Answer 16

region of the genome that we’re not clear what they do, they’re not coding for protein or RNA, likely to be regulatory

Question 17

Exons

Answer 17

coding for protein only constitute 1-2% of the genome

Question 18

Introns

Answer 18

non-coding region of the genome and constitutes a larger fraction of the genome

Question 19

Genes

Answer 19

RNA coding and regulatory sequences, introns and exons (still the smaller fraction of the genome in total)

Question 20

The genome unravelled

Answer 20

DNA organised into chromosomes.
At sequence level, then whole level of structure on top (RNA), DNA, DNA wrapped around nucleosomes to form chromatin, then bound and coiled again to form the chromosomes = Super coiled DNA molecule

Question 21

The power of 7 billion people

Answer 21

• Given known mutation rates, it’s almost certain that every possible single base change compatible with life exists in a living human

Question 22

2 papers looking at variation

Answer 22

Exome Aggregation Consortium (ExAC) and Genome Aggregation Database (gnomAD)

Question 23

Exome Aggregation Consortium (ExAC)

Answer 23

• 60,706 exomes
• Began in 2012, first release Oct 2014
• Preprint in Oct 2015
• Published in May 2016

Question 24

Genome Aggregation Database (gnomAD)

Answer 24

• 125,748 exomes and 15,708 genomes
• Began in 2016, first release Oct 2016
• Latest data release 2020
• 4 papers in Nature in August 2020 - documented the level of variation at the single base level

Question 25

Loss of function variants =

Answer 25

variants that cause a stop-codon to be gained or effect an essential splice or cause a frameshift in the protein – this causes loss of function of protein – these are very deleterious but also common.

Question 26

Comparative Genomics

Answer 26

Living organisms have a different number of chromosomes. No correlation between number of chromosomes and complexity of organism

Question 27

transcriptome

Answer 27

Areas of the genome that are transcribed into RNA