Topic 3 - Genetics Flashcards
What is DNA?
deoxyribose nucleic acid
- polymer made up of many subunits (nucleotides)
Where is DNA in a cell?
nucleus
What is the structure of DNA?
double helix formed by complementary strands of nucleotides held together by hydrogen bonds
Describe the relationship between chromosomes, DNA and genes.
DNA is packed tightly into chromosomes which code for genes and traits.
What is a nucleotide?
A nucleotide is a subunit in DNA that is made up of 3 parts.
- phosphate
- deoxyribose sugar
- nitrogenous base
they are joined together by sugar phosphate groups which forms a backbone
What are the 4 bases in DNA? What base pairs with what?
adenine
thymine
cytosine
guanine
A+T, C+G
What bonds hold together the bases in DNA?
hydrogen bonds
What is protein synthesis?
how genes make a protein
- transcription (DNA -> mRNA)
- translation (mRNA -> protein)
What are the 3 steps involved in transcription?
- initiation
- elongation
- termination
What is initiation?
- RNA polymerase binds
to a part of a gene called the promoter - which causes the DNA to unwind so the enzyme can read the bases in one of the strands
- The enzyme then makes a strand of mRNA with a complementary sequence of bases
What is elongation?
- complementary nucleotides are added to synthesise an mRNA strand
- RNA polymerase reads the unwound DNA strand and builds the mRNA molecule, using complementary base pairs
What is termination?
- ending of transcription, and occurs when RNA polymerase
crosses a termination sequence in the gene - the mRNA strand is complete, and it detaches from DNA.
Where does transcription occur?
nucleus
Where does translation occur?
ribosome
What is the 1st step of translation?
mRNA moves through the nuclear pore to the cytoplasm
What is the 2nd step of translation?
mRNA attaches to the ribosome and the ribosome moves along the mRNA strand reading the codons, translation begings at AUG
What is the 3rd step of translation?
transfer RNA (tRNA) molecules ferry the amino acids to the mRNA at the ribosome
What is the 4th step of translation?
tRNA links with the ribosome and matches its anticodon with the codon of the mRNA
What is the 5th step of translation?
a peptide bond forms between the adjoining amino acids, forming a polypeptide
- tRNA is removed to be used again
What is the 6th step of translation?
protein production stops when the STOP codon is reached
don’t write stop
mRNA breaks away from the ribosomes
What is mRNA?
messenger RNA
How is mRNA paired with DNA? Bases?
Adenine + Uracil
Cytosine + Guanine
What is the role of the ribosome?
making proteins
What is a codon?
A sequence of three DNA or RNA nucelotides in mRNA
What is an anticodon?
sequence of 3 nucleotides in tRNA that corresponds to an mRNA amino acid
What is tRNA + role?
transfer RNA
- ferry amino acids to the mRNA at the ribosome
What is a mutation?
Mutations are changes in genetic
material (DNA and genes)
When do mutations occur?
- Errors in DNA replication
- enduced by mutagens (environmental factors that change DNA)
What are mutagens?
- X-rays/radiation
- Chemicals, poisons
- UV light
- Viruses
What is point mutation? eg
change in a single base pair of DNA by substitution, deletion, or insertion of a single nitrogenous base. . eg.Cystic fibrosis, sickle cell anemia
How is a point mutation different from a deletion/addition mutation?
point mutations is when one base pair is replaced by another and insertions or deletions is when nucleotides are added or removed.
How do mutations impact protein synthesis?
- DNA affected
- mRNA not copied properly
- codes for wrong amino acid
- formation of incorrect protein/part of polypeptide is missing/no functioning protein
What are some diseases that are caused by genetic mutations?
Huntington’s Disease
Sickle cell anemia
How is huntington’s disease caused and what are some symptoms?
- Mutations in a gene
- DNA segment of cytosine, adenine and guanine that appear multiple times in a row. (normaly 10-35 times, HD 120 times)
- depression
- stumbling and clumsiness
- mood swings
How is sickle cell anemia caused and what are some symptoms?
- Only one amino acid changes in the haemoglobin
- haemoglobin still functions but it folds differently, changing the shape of the red blood cell, and affecting the way it can carry oxygen.
- swelling of hands and feet
- Vision problems
- delayed growth or puberty
