Flashcards in Genetics And Division Deck (43):
What is DNA?
A double helix, each of the two DNa strands is made up of small molecules called nucleotides
Name the four bases in DNA
What does each base of DNA form?
Hydrogen bonds to a base of the other side, this keeps the two strands tight together
Which two bases join together?
Adenine (A) and thymine (T)
Cytosine (C) and guanine (G)
Why are the bases in DNA a certain pair?
They complement each other in shape
A section of DNA that codes for a particular protein is called
How do proteins have different functions?
The chains of amino acids are different orders and numbers to give each protein a different shape
What decides the order of amino acids in a protein?
The order of the bases in a gene
Where are DNA molecules found?
In the nucleus of a cell
Where does protein synthesis happen?
In the cytoplasm at organelles called ribosomes
What is the copy of a gene made from?
From a molecule called messenger RNA
What is RNA made from?
What does a cell do when it needs a particular protein?
Makes a copy of the gene that's smaller than the DNA so it can move in to the cytoplasm where it's used to make the protein
There is no thymine (T) in RNA, so what replaces it to join adenine (A)?
What happens when the bases on the RNA nucleotides have paired up with the bases on the DNA strand?
The RNA nucleotides join together to make an mRNA molecule.
What is DNA made up of?
Nucleotides containing bases
What do three bases in a row code for?
One amino acid
How many bases code for one amino acid?
Three (a triplet)
The order of the bases in the DNA of a gene determines what?
The order of bases in its mRNA copy, and that determines the order of amino acids in a protein
What are mutations?
Changes to the base sequence of DNA
What can a change in the amino acids cause?
A different protein to be produced, sometimes it can be harmful
What are mutagenic agents?
Factors that increase mutations, such as UV radiation in sunlight
How can mutations cause cancer?
Cell division is controlled by proteins, is mutations occur in the genes for these proteins, they can alter so they no longer work. This can lead to uncontrolled cell division, developing a tumour (cancer)
How can mutations cause genetic disorders?
Mutations that result in altered genes and proteins can be inherited such as cystic fibrosis
Where and in what cells is DNA found?
In the nucleus of eukaryotic cells
How many homologous pairs of chromosomes do humans have?
What are alleles?
Different versions of a gene
Are homologous pairs of chromosomes identical? Why?
Yes, they are the same size and carry the same gene
Why is the name of the region where two identical chromatids are joined?
What is mitosis needed for?
Growth and repair
What type of reproduction involves mitosis?
What happens in asexual reproduction?
A single organism produces offspring by dividing into two organisms, all offspring are genetically identical to each other and to the parent
Explain what happens in mitosis (briefly)
The DNA copies itself, then divides once
What are the 5 stages of mitosis?
Before the cell divides, each chromosome much replicate so each new cell has a full copy of DNA
Mitosis can now begin, each DNA molecule becomes compact, so the chromosomes can now be seen by the microscope and appears as two chromatids
The nuclear membrane breaks down and the chromosomes line up along the middle of the cell
The centromeres split and the chromatids separate
A nuclear membrane forms a round each set of chromatids and the cytoplasm divides
What production is meiosis?
Describe sexual reproduction
The offspring are genetically different from each other and their parents. This produces variation
How many cells are produced when a cell divides by mitosis?