Cell Biology Flashcards
What is a genome?
complete collection of genetic material within an organism
What is genomics?
DNA structure of genes and their localisation within the genome
What is protenomics?
characterisation of biological processes from measurement of protein expression localisation and post translational modification
Describe the human genome
-sequences in 2003, 10% of DNA in mammals encodes genome
-repeating sequences
-3 billion base pairs
-30,000 genes
What is pharmacogenomics?
effects of chemicals on gene transcription and protein expression
What can profiling an individuals genome (sequencing) do?
-understand inherited basis for congenital disorders
-predict our chance of developing certain diseases
What are the 2 types of mutations?
-germline
-somatic
Describe germline mutations
gonadal cells that become eggs/sperm carrying the mutation within their DNA
Describe somatic mutation
-cells of body carrying a mutation
-underlies monogenic disorders- disorders controlled by a single gene
What are the different types of genetic disorders?
-single gene disorders
-chromosomal disorders
-polygenic disorders
-somatic disorders
What is a single gene disorder?
mutation in a single gene e.g. cystic fibrosis
What is a chromosomal disorder?
change, gain, loss or exchange of chromosome elements e.g. downs syndrome
What is a polygenic disorder?
combined effects of mutations in multiple gene or in combination with environmental factors e.g. natural tube defects
What is a somatic disorder?
non-germline disorder such as uncontrolled growth e.g. cancer
Describe the molecular structure of DNA
-double helix=compact structure
-DNA length shortened by interaction w/ histone proteins
-HP contains AA’s arginine and lysine (+ charged, pH 7.4)
- so - charge phosphate groups on DNA more attracted to arginine residues than lysine
Describe histone H1
-globular (NH2) and arm (COOH) domains
-H1 binds to nucleosome via globular domain
-the arm domain binds to other H1 globular domains
Describe chromosomes
-genetic info stored within DNA
-blueprint for human proteome
-genes located on chromosome
Describe somatic cells
-46 chromosomes (diploid)
-22 autosomal pairs
-one from each parent
-2 gender chromosomes
Describe chromosome 1
-largest
-250 mega bases of DNA
Describe chromosome 2
240 Mb of DNA
Describe chromosome 21 + 22
55 + 60 Mb of DNA
Describe the X + Y chromosome
140 Mb of DNA (X)+ 60Mb DNA (Y)
Describe the female XX chromosome
-only one is transcriptionally active (lyonisation)
-avoids 2 copies X transmitted gene products
-methylation of X chromosome inactivates the same chromosome
What is chromosome karotyping?
-visual inspection of chromosomes in metaphase
-use spindle toxins e.g. colchicine
Describe the centromere of a chromosome
-middle (metacentric)
-towards one end (acrocentric): shorter arm= p arm, longer arm= q arm
What are the stripes that appear on stained chromosomes?
-dark bands: tightly coiled chromatin= transcriptionally inactive
-clear bands: not so tightly coiled euchromatin transcriptionally active
What are the different types of chromosome abnormalities?
number + structure
What are the different types of number abnormalities?
-polyploidy
-aneuploidy
-monosomy
-trisomy
Describe the polyploidy number abnormality
-additional set of chromosomes
-multiples of 23
Describe the aneuploidy number abnormality
-missing set of chromosomes
-multiples of 23
-not compatible with life
Describe the monosomy number abnormality
-only one copy of a chromosome in diploid cell
-rarely compatible with life
Describe the trisomy number abnormality
-3 copies of a chromosome in diploid cell
-trisomy 21 (downs syndrome)= most common
What are the 3 types of structure abnormalities?
-duplications
-inversions
-isochromosome
-translocations
-deletions
Describe the duplication structure abnormality
unequal crossover
Describe the inversion structure abnormality
-2 breaks in chromosome, free portion rotates
-involves centromere= pericentric
-not involve centromere= paracentric
-can cause haemophilia
Describe the isochromosome structure abnormality
-form after chromosome pairs split during telophase
-new chromosomes have only short/long arms
Describe the translocation structure abnormality
-exchange of genetic material between chromosomes = reciprocal translocation
-short p arms of chromosomes are long and long q arms fuse to form one large chromosome
Describe the deletion structure abnormality
-loss of genetic material when breaks in chromosomes occur
-e.g. cri-du-chat syndrome= child’s distinctive cry, partial loss of chromosome 5 p arms
What are telomeres?
-end of each chromosome, non coding
-copies of hexameric nucleotides
-shorten with cell age
What do telomeres maintain/promote?
-chromosome stability
-complete DNA replication
-aid chromosome pairing
