Topic 3 - Genetics Flashcards
What is DNA?
Deoxyribonucleic acid is a complex molecule that contains all of the information necessary to build and maintain an organism.
Where is DNA in a cell?
Cell nucleus
What is the structure of DNA?
A double helix formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs.
Describe the relationship between chromosomes, DNA and genes.
Chromosomes carry DNA in cells. DNA is responsible for building and maintaining your human structure. Genes are segments of your DNA, which give you physical characteristics that make you unique
What is a nucleotide?
The basic building block of nucleic acids (RNA and DNA). It contains a sugar molecule, attached to a phosphate group and a base.
What are the 4 bases in DNA? What base pairs with what?
Adenine, Thymine, Cytosine and Guanine
- A + T
- C + G
What bonds hold together the bases in DNA?
Hydrogen bonds
What is RNA?
Ribonucleic acid is single-stranded and does not have to stay in the nucleus.
Describe how DNA and RNA are similar and how they differ
Similarities
-RNA and DNA are both made of nucleotides
Differences
-RNA is single stranded, DNA is double stranded.
-RNA contains ribose sugar, DNA contains deoxyribose sugar
-RNA has base pairs AUCG, DNA has base pairs ATCG
What is protein synthesis?
The process in which DNA cells make proteins.
What are the 2 steps of protein synthesis?
-Transcription (DNA to mRNA)
-Translation (mRNA to protein)
Transcription
-DNA to mRNA
-Occurs in the nucleus
-It is broken into 3 steps
1. Initiation
2. Elongation
3. Termination
-After these three steps, the mRNA is ready to leave the nucleus, travel into the cytoplasm, attach to a ribosome and be TRANSLATED into a protein
Initiation
-Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds into a region of gene called the ‘promoter’
-This signals the DNA to unwind so the enzyme can ‘read’ the bases in one of the DNA strands (template strand)
-The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases
Elongation
-Elongation is when 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
-Adenine pairs with Uracil and Cytosine pairs with Guanine
Termination
-Termination is the ending of transcription, and occurs when RNA polymerase crosses a termination sequence in the gene
-The mRNA strand is complete, and it detaches from the DNA
Translation
-mRNA to protein
-Occurs in the cytoplasm
-It is broken into 6 steps
Step 1
The mRNA moves through the nucleus pore into the cytoplasm
Step 2
-The mRNA attaches to the ribosome. The ribosome moves along the mRNA strand, reading 3 nucleotides (codon) at a time
-Translation begins at the START codon. The START codon is always AUG
Step 3
Transfer RNA molecules (tRNA) move the amino acids to the mRNA at the ribosome
Step 4
tRNA links with the ribosome and matches its anticodon with the codon of the mRNA
Step 5
A peptide bond forms between the adjoining amino acids, forming a polypeptide. The tRNA is removed to be used again.
Step 6
-The protein production stops when a STOP codon is reached. The mRNA breaks away from the ribosome.
-STOP codons are UAA, UGA, UAG
-They are stop codons because they don’t code for an amino acid
What is mRNA?
-Messenger Ribonucleic Acid is single stranded molecule that carries the instructions to make proteins.
-main molecule that is associated with transcription
How is mRNA paired with DNA?
During transcription, the enzyme RNA polymerase uses DNA as a template to produce a pre-mRNA transcript
