MGD L1 Flashcards
Describe what is meant by “central dogma” of molecular biology
Flow of genetic material in a biological system
State two examples of nucleic acids
- DNA (deoxyribonucleic acid)
- RNA (ribonucleic acid)
What is a nucleic acid?
Nucleic acids are polynucleotides
(linear polymers of nucleotides)
What is a nucleotide?
Basic building block of nucleic acids
Consists of
1. pentose sugar (ribose, deoxyribose)
2. Phosphate group
3. Nitrogen containing base
State the nitrogenous bases in DNA and RNA
Describe the primary structure of a polynucleotide
- Within nucleotide, pentose sugar + nitrogenous base are connected via glycosidic bond
- Nucleotides are joined by phosphodiester bonds
- Polynucleotide chain has two distinct ends and polarity: 5’ → 3’
Describe the secondary structure of a polynucleotide
Two anti-parallel, complementary strands
Describe the structure of DNA
- Two complementary anti-parallel polynucleotide chains
- Each consists of a sugar phosphate backbone + nitrogenous base
- Nitrogenous base pairing is specific. A=T C=G
- DNA is negatively charged
Why is DNA negatively charged?
- Could be exam question
What is the human genome?
Consists of info contained in DNA in one set of human chromosomes
How many chromosomes are there in each diploid cell?
46 chromosomes
22 pairs of autosome chromosomes
1 pair of sex chromosomes
How long is the DNA in each diploid cell (if stretched)?
2m
What is a gene?
Sequence of nucleotides in DNA
Encodes synthesis of protein, RNA or gene product
State the two types of genes
Protein-encoding genes
Protein non-encoding genes (most DNA is non-encoding, containing LINEs - Long Interspersed Nuclear Elements - SINEs - Short Interspersed Nuclear Elements)
What was the Human Genome Project?
Human genome project
The Human Genome Project (1990 -2003) was the international research effort to determine the DNA
sequence of the entire human genome with the primary goal to discover the complete set of human
genes and make them accessible for further biological study.
DNA packaging
How is it possible that DNA in each diploid cell, that is 2 m long, can fit in the nucleus that is 5 - 10 mm?
DNA PACKAGING
- DNA in nucleus exists in complex with histones, forming chromatin that functions to package long DNA molecules into more compact, denser structures (DNA in chromatin is supercoiled)
2.2x of the following histone proteins:
H2A
H2B
H3
H4
These make up a histone octamer.
This binds + wraps apporximately 1.7 turns of DNA.
The addition of H1 histone protein leads to 2 full turns around octamer, forming chromatosome
What is the repeating structural (and functional) unit of chromatin?
NUCLEOSOME (contains 8 histone proteins)
What are chromosome territories?
Uncondensed chromosomes occupying regions of nucleus
How do chromosomes reflect variations in gene expression patterns?
Positions of chromosomes relative to one another differs from cell to cell.
During which stage if cel division are chromosomes most compacted?
Metaphase (in mitosis)
Describe the structure of a chromosome
- Each chromosome consists of a short arm and a long arm connected by a centromere
- A chromatid is one of two identical halves of a replicated chromosome
P arm
Q arm
- pay attention to diagram
