Variation & Selection Flashcards
what does DNA stand for
DNA = Deoxyribonucleic Acid
what is the monomer of DNA
DNA is a polymer
The monomer of DNA is nucleotides
what structure does DNA have
DNA has the structure of a double helix (two strands coiled together)
what is DNA
DNA is genetic material that is found is inside the nucleus, in chromosomes
what are chromosomes
Chromosomes are DNA wrapped around a protein called histones
where are genes located
Genes are located on chromosomes inside the nucleus
what are genes
Genes = genetic material which codes for specific proteins
how do genes control living organisms
By controlling which proteins our cells make, genes control living organisms’ features and characterisitics
why are cells identical when mitosis
When cells divide, each cell is genetically identical
This is because DNA can replicate - when mitosis takes place, DNA is replicated
what is a nucleotide made up of
Each nucleotide is made up of: deoxyribose (sugar molecule), phosphate molecule, a nitrogen-containing group called a base)
what backbone does DNA have
DNA has a sugar phosphate backbone
what are the 4 bases
ATCG (At Charlie’s Gateshead)
A = Adenine
T = Thymine
C = Cytosine
G = Guanine
what bases are complimentary
AT are complimentary
CG are complimentary
When do complemetary bases pair up
The complementary bases always pair up when the two strands of DNA come together - they cannot bind to other bases
This is called the base-pairing rule
what bonds form between the bases
When they pair up, hydrogen bonds form between the bases
which chemical can replicate itself in humans
DNA is the only chemical that can replicate itself identically
This means that it can be passed down through generations of cells as a genetic code
what is the first step before mitosis
In cell division, the first step before mitosis is replication⟶ DNA makes copies of itself - so each daughter cell produced in mitosis is genetically identical
how does DNA replicate (4)
The process of DNA replication:
1. Polynucleotide strands of DNA separate
2. Each original strand of DNA acts as a template strand
3. DNA polymerases use the base-pairing rule to assemble free nucleotides into two new strands of DNA
4. Two identical strands of DNA are formed - each new strand contains one original parent strand and a new complementary strand
which DNA strand codes for protein
Only one of our strands of DNA codes for proteins
We call this the template strand
what protein does the cell make the most
Most of the proteins that the cell makes are enzymes –> they control reactions within the cell
what are some examples of structural proteins (3)
Examples of some structural proteins that are made are: keratin (in the skin) and myosin (in the muscles)
Some other proteins with important roles in the body are haemoglobin, and hormones
Proteins are chains of amino acids
what is a triplet code
Triplet code = three bases that code for one amino acid
what is a gene
A gene is a section of DNA for all the triplet codes for one protein
how many natural amino acids are there
There are around 20 natural amino acids
what type of code is DNA how does it affect the proteins in other animals , think about other animals
and each of these amino acids have the same triplet code in almost all organisms
The DNA code is a universal code
where does protein synthesis happen
DNA stays in the nucleus but protein synthesis happens in the ribosomes which are in the cytoplasm
why cant dna be tranposrted as a whole
Our nuclear pores (holes in the nuclear membrane) are too small to transport our entire DNA out of the nucleus into cytoplasm
how is DNA transported
SO, for proteins to be made, the genetic code is first copied, and then transferred out of the nucleus, through the nuclear pores, into the cytoplasm
This is carried out by a DIFFERENT nucleic acid - RNA
what is rna
RNA = ribonucleic acid
differences between dna and rna (5)
Ribose and deoxyribose (the sugars) are very similar in structure
The bases Uracil and Thymine are also very similar in structure
The 3 main differences between DNA and RNA:
1. RNA contains the base Uracil (U) instead of Thymine (T)
2. DNA contains the sugar deoxyribose and RNA contains the sugar ribose
3. DNA is a double helix, RNA is just a single strand
what are the 2 types of RNA involved in protein syntehsis and what do they do (2)
2 Types of RNA involved in protein synthesis:
messenger RNA (mRNA) = makes a copy of the DNA code (think of it as a messenger between the nucleus and ribosomes)
transfer RNA (tRNA) = these TRANSFER amino acids from our cytoplasm to our ribosomes, to make the protein
what is another 3rd RNA
There is a 3rd RNA called ribosomal RNA (rRNA) = found in ribosomes - ribosomes are made of rRNA and protein
what are the stages in protein synthesis
The two stages of protein synthesis are:
1. transcription
2. translation
Transcription = when a copy of the genetic code for the protein is made and transported to the ribosome
mRNA = a copy of the genetic code
Transcriptions:
1. Part of the DNA double helix unwinds
2. the DNA double helix unzips - the bonds between the bases are broken, allowing the two strands to separate from each other. This exposes the bases along the template strand
3. The template strand of DNA is used to form mRNA - RNA nucleotides are lined up along the template strand according to the base pairing rule
4. In the base pairing rule, Thymine is replaced with Uracil in RNA molecules
5. These RNA nucleotides line up in the correct order to form mRNA
6. The sugar-phosphate backbone is formed for the mRNA molecule by bonds forming between the ribose and phosphate groups
7. Once mRNA molecule is complete (when the entire section of DNA coding for the protein has been transcribed), it leaves the DNA, out of the nuclear pores, into the cytoplasm, to the ribosomes
8. DNA needs to zip up again
In transcription, our DNA triplet codes have been converted into RNA triplet codes
