CB3: Genetics Flashcards
What is a zygote?
A single fertilised egg cell
What is DNA?
Deoxyribonucleic acid. The material inside the nucleus of cells, carries the genetic information of a living being.
Define genes
The basic unit of genetic material inherited from our parents. A gene is a section of DNA that controls part of a cell’s chemistry - particularly protein production
Define chromosomes
The structure made of DNA that codes for all the characteristics of an organism.
What is the difference between a diploid cell and a haploid cell?
A diploid cell contains 2 sets of 23 pairs of chromosomes (46 individual chromosomes) whereas a haploid cell only contains 23 chromosomes (half the amount)
Under what circumstances must a cell be haploid?
When the cell is a gamete (sex cell) it is haploid because two gametes combine to make a diploid zygote
What type of cell division produces:
a) diploid cells?
b) haploid cells?
a) Mitosis
b) Meiosis
What is the difference between mitosis and meiosis?
Mitosis produces two diploid genetically identical cells whereas meiosis produces four genetically different cells. Mitosis is used during asexual reproduction whereas meiosis is used during sexual reproduction
What are the steps in meiosis?
- The gamete-making cell has two sets of chromosomes
- The chromosomes replicate and the copies stay stuck to each other
- The cell divides into 2 and then 2 again. Each of the four daughter cells ha a copy of 1 chromosome from each pair. They are haploid
What is a double helix and what connects it?
The shape of a DNA molecule with two strands twisted together like a spiral. They are connected by weak hydrogen bonds between complementary base pairs
What is a nucleotide and what is it made up of?
The monomer of DNA. Made up of a base, a phosphate group, and a sugar
Define genome
The copy of all an organisms DNA
What are the base pairs in DNA?
A-T
C=G
What do the order of the bases affect?
Controls the order in which amino acids are joined up to make a specific protein or enzyme molecule
Define alleles
Different versions of the same genes (eg eye colour). A body cell contains two copies of every gene
What is the difference between heterozygous and homozygous?
Heterozygous: if the two copies of the gene are different
Homozygous: if the two copies of the gene are the same
What is the difference between a dominant and a recessive allele?
A dominant allele will always be expressed no matter if the gene is heterozygous or homozygous, whereas a recessive allele will only be expressed in a homozygous gene. A dominant allele is written with a capital letter whereas a recessive gene is written with a lowercase letter
What is a genotype?
All of the alleles in an organism
What is a phenotype?
The alleles that have been expressed
What are the two sex chromosomes and what are the combinations for males and females?
X and Y
Male: XY
Female: XX
Define mutations
A random and spontaneous change in a gene or a chromosome. Most have no effect on the phenotype
Define variation
The differences between organisms.
Define natural selection and give another name for it
Organisms better suited for an environment are more likely to survive and pass on their genes. It is also called the survival of the fittest
What are the causes of mutations?
- ionising radiation
- chemical mutagen such as tar from cigarette smoke
State and define the two types of variation
Genetic variation: caused by inherited alleles during sexual reproduction
Environmental variation: caused by the environment giving acquired characteristics
What are the two groups that variation can be grouped into?
Continuous variation: data that can be any value in a range
Discontinuous variation: data that can only take a limited set of values
What is a normal distribution?
A bell shape curve on a graph
