Genomics structure and function of the human genome Flashcards
What is the short and long arm in chromosmes?
- p arm is the short arm
- q arm is the long arm
What are the 4 types of chromosomes and what does it depend on?
Depends on where the centromere:
1. Metacentric
2. Sub-metacentric
3. acrocentric
4. telocentric
What are the 3 key features scientists use to identify chromosomes?
- Size
- Banding pattern
- Centromere position
What do chromosomes usually exist as?
Usually exist as chromatin
What is DNA double helix bound to?
DNA double helix bounds to histones
What forms nucleosome?
Octamer of histones form nucleosome
What histones are present in the octamer that forms the nucleosome?
- 2x(H2A, H2B, H3 and H4)
What is histone H1 for in nucleosome?
H1 binds to these nucleosomal core particles close to the DNA entry and exit sites and protects the free linker DNA
What is euchromatin?
Extended state, dispersed through nucleus
What does euchromatin allow in terms of gene expression?
Allows gene expression
What state is heterochromatin and hows the gene expression like?
Highly condensed, genes not expressed
Steps in compaction of chromosome
Chromosome –> chromatin fiber –> histones –>Beads on a string(DNA wound on nucleosomes)–> double helix
What do centromeres keep together?
Keep sister chromatids together
What do centromeres attach to?
Attach to microtubules during cell division
What are centromeres rich in?
Rich in heterochromatin
What is the repetition like in centromeres?
Highly repetitive
What do telomeres protect?
Telomeres protect the ends of the chromosomes
What does telomerase repair?
Telomerase repairs telomeres
but is only active in certain cell
types
What can telomerase being activated in the wrong cell lead to?
If telomerase is switched on in
the wrong cells this can lead to
cancer
What are protein-coding genes known as?
Exomes
What do exons code for?
code for amino acids except for Untranslated Regions (5’UTR & 3’UTR)
What do UTR contain and what is it important for?
contain regulatory elements (important for control of protein synthesis)
What are introns?
non-coding section of gene between exons
What is the promoter region?
5’ of gene; contains important regulatory
elements for transcription
How many autosomes and sex chromosomes are there in the nuclear genome?
-22 pairs of autosomes
-1 pair of sex chromosomes
What are transcribes units in the nuclear genome also known as?
Genes
How many bases are in the mitochondrial genome?
16Kb
What does the D-loop in the mitochondrial genome contain?
Contains promoters for light and heavy strands
How many coding genes are there in mitochondrial genome?
13 coding genes
How many non-coding genes are there in the mitochondrial genome?
24 non-coding genes
What type of inheritance is mitochondria and why?
Maternal inheritance
-This is because only OVA provide mitochondria
What are the purines in DNA?
-Adenine
-Guanine
What are the pyrimidines in DNA?
-Cytosine
-Thymine
What is the epigenome and what are examples?
-Chemical compounds that attach to DNA or histones and can affect gene activity
-E.g. DNA methylation, histone acetylation
How does the epigenome affect gene activity?
- Alter chromatin structure
- Recruit histone modifiers
- Repress transcription
- Genome-wide pattern established at fertilisation
- Important for differential gene expression (transcription)
- Responds to environmental cues (cellular and external)
What is gene expression controlled by?
Controlled by DNA sequence and epigenome
What is differential gene expression in time?
- Development (i.e. embryos versus adults)
- In response to hormones, infection, other signals
What is spatial differential gene expression?
Different tissues/cells express different genes (e.g. brain vs liver)
What can a failure to regulate gene expression tightly lead to in metabolism?
Metabolic disease
What can failure to regulate gene expression tightly lead to in cell shape/motility?
Metastasis
What can failure to regulate gene expression tightly in cell differentiation?
Congenital disorders
