DNA & Inheritance Flashcards
1
Q
Genome
A
- The complete set of chromosomes (46) and all the information within them.
2
Q
Gene
A
- A unit of DNA that encodes for particular proteins.
3
Q
Histone
A
- Type of protein that binds to DNA, giving chromosomes their shape and controls the activity of genes.
4
Q
Chromatin
A
- Formation of DNA when cell is not dividing
5
Q
Mitochondrial DNA (mtDNA)
A
- Small circular chromosomes found within the mitochondria.
- Are maternally inherited.
- 37 genes in total, 24 encode for making of tRNA molecules with the other 13 containing instructions for some of the enzymes needed for cellular respiration.
6
Q
Differences between DNA and RNA
A
- RNA is single stranded and DNA is double-stranded.
- RNA can fold upon itself whilst DNA cannot.
- RNA has Uracil instead of Thymine, which DNA has.
- RNA can fit through nuclear pores whilst DNA cannot.
7
Q
Messenger RNA
A
- Made in the nucleus, takes genetic code into the cytoplasm to be read by a ribosome.
8
Q
Transfer RNA
A
- Able to carry a specific amino acid and therefore plays a vital role in protein synthesis.
9
Q
Ribosomal RNA
A
- rRNA ensures correct alignment of tRNA, mRNA and ribosome. Has an enzymatic role in formation of peptide bonds between amino acids.
10
Q
Protein Synthesis: Transcription
A
- Process in which genetic instructions are copied from DNA to an mRNA molecule. The transcription is triggered by chemical messengers that enter the nucleus from the cytosol and bind to the DNA at the relevant gene. Thus causing an enzyme called RNA Polymerase to begin the process of making mRNA.
- Helicase unwinds the double-stranded DNA molecule. This can occur at roughly 17 base pairs at a time. RNA Polymerase then copies the bases on one strand of DNA to make a complementary mRNA strand.
- At the end of a gene, a sequence of bases tell the RNA Polymerase to stop copying and as a result the mRNA molecule is released. Often other RNA Polymerases will follow behind the first, so that many copies are made.
- As bases will always form complementary pairs, the order of bases on coding strand will be same as in the mRNA molecule, except for thymine - uracil swap.
11
Q
Protein Synthesis: Translation
A
- The production of a protein using the information coded in the mRNA molecule. In the cytosol, a ribosome attaches to one end of the mRNA molecule at a particular sequence of bases called the start codon. This ensures that the ribosome attaches to the correct end of the mRNA.
- The ribosome then moves along the mRNA three bases at a time. Each group of three is called a codon and makes an amino acid. The start codon AUG, encodes for the amino acid methionine, meaning that every protein begins with methionine. However it may be removed later.
- As the ribosome reads the codons on mRNA, the tRNA molecules with complementary bases join to the mRNA. The sequence of three bases matching the codon is called an anticodon. The amino acids carried by the tRNA are joined so that the protein is assembled with the amino acids in the correct sequence. For each bond formed between the amino acids, the energy from the breakdown of one ATP molecule is required. Once tRNA has delivered its amino acid, it detaches from the ribosome and can then pick up another amino acid from the cytosol.
12
Q
DNA Replication
A
- First stage in DNA Replication is when the two strands of the DNA molecule are separated by an enzyme known as helicase.
- Each strand of the separated contains half the original information. As base pairs can only pair with one other, this then means that the new strand is identical to the other original.
- Two enzymes that aid in the synthesising of the two new strands. These enzymes are DNA polymerase, which adds new nucleotides to the new strand, and DNA ligase, which joins sections of DNA together.
- RNA Primase aids DNA Polymerase by laying down a primer from which the DNA Polymerase can then start adding free nitrogenous bases from. There are two strands in the DNA when DNA Replication is occurring, the lagging and leading strand. Firstly, DNA Polymerase moves in the 3’ to 5’ direction. So the leading strand is able to move in this direction with no problems but on the lagging strand RNA Primase needs to circulate to aid the DNA Polymerase which can only move in one direction. These then leaves behind fragments of strands. These fragments are called Okazaki fragments. After DNA Replication is done, the enzyme ligase comes and bonds the base pairs together. This then result with 2 semi-conservative strands.
13
Q
Allele
A
- An alternative form of a gene.
14
Q
Dominant Allele
A
- An allele that masks the affect of another allele.
15
Q
Recessive Allele
A
- An allele that is masked by the alternative, dominant allele.
