Genetics ( Test 3) Flashcards
What is sexual reproduction
The process involving the fusion of the nuclei of two gametes to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other
Names of sex cells in plants and animals
Animal- Sperm and Ovum
Plant- Pollen nucleus and Ovum
How many chromosomes does a gamete have and what do we call them
23 chromosomes ( haploid)
What is asexual reproduction
The process resulting in genetically identical offspring (clones) being produced from one parent
What is binary fission
When bacteria produces exact genetic copies of them self by asexual reproduction which creates 2 identical daughter cells.
What type of cell division is needed for asexual reproduction
Mitosis
What type of cell division is needed for sexual reproduction
Meiosis
What is a genome
The entire set of the genetic material of an organism
What is a gene
A section of DNA that codes for a particular sequence of amino acids which form proteins
What is DNA
The genetic material found in the nucleus of the cell
What is DNA made up of
DNA is a polymer made up of two strands coiled around to make a double helix
What is a nucleotide
A nucleotide is made of a sugar and a phosphate group, with one of four different bases, A, C, T or G, attached. The nucleotides join together, forming two strands. These form a double helix structure. The double helix is held together by weak hydrogen bonding between complementary base pairs.
Describe the role of nucleotides in the structure of DNA
The phosphate and sugar section of the nucleotides form the ‘backbone’ of the DNA strand (like the sides of a ladder) and the base pairs of each strand connect to form the rungs of the ladder
Name the 2 stages that occur in protein synthesis
Transcription and translation
What is transcription
It takes place in the nucleus and the strand of mRNA that is formed moves out of the nucleus and into the cytoplasm.
What is translation
It takes place in the cytoplasm when the mRNA strand attaches to the ribosome
Name the complementary base pairs in mRNA
Cytosine and Guanine
Adenine and Thymine
Name the complementary base pairs in tRNA
Cytosine and Guanine
Adenine and Uracil
Describe what occurs in translation
This stage of protein synthesis occurs in the cytoplasm. The ribsome reads the code on the mRNA in groups of 3, each triplet of bases/ codon codes for an amino acid
Why must DNA first be transcribed into mRNA before it can be translated into a protein
DNA cannot travel out of the nucleus to the ribosomes (it is far too big to pass through a nuclear pore) so the base code of each gene is transcribed into an RNA molecule called messenger RNA (mRNA).
What is an allele
A variation of a gene which can be dominant or recessive
Homozygous meaning
If the two alleles of a gene are the same we describe the individual as homozygous
Heterozygous meaning
If the two alleles of a gene are different we describe the individual as heterozyous
Genotype meaning
The combination of alleles that control each characteristic
Phenotype meaning
The observable characteristics of an organism
Dominant allele meaning
A dominant allele is always expressed even if only one copy is present
What is monohybrid inheritance
Inheritance of characteristics controlled by a single gene
Is the male or female responsable for determining the sex of the child?
Male because female chromosomes are XX whereas male chromosomes are XY
What are the four main blood groups?
A, AB, B, O
Is blood type O the recessive or dominant allele?
Recessive
Explain what polygenic means and give an example
Characteristics that are controlled by more than one gene an example of this is eye colour
Define variation
Differences between individuals of the same species
What is continuous variation?
Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale. Examples include height, mass, finger length
What is continuous variation?
Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale. Examples include height, mass, finger length
What is discontinuous variation
Discontinuous variation is when there are distinct differences for a characteristics. For example, people are either blood group A, B, AB or O
How is continuous variation found on a graph
It has a bell shaped curve
Is discontinuous variation usually caused by genetic variation or environmental variation or both?
Genetic variation
Is continuous variation usually caused by genetic variation or environmental variation or both?
Both, genetic and environmental variation
Define a zygote
Fertilisation is the fusion of the nucleus of a male gamete with the nucleus of a female gamete, producing a new cell called a zygote
Define phenotypic variation and what can it be caused by
Phenotypic variation is the difference in features between individuals of the same species. It can be caused by genetic and environmental variation.
Compare mitosis and meiosis
Meiosis produces four genetically different daughter cells while mitosis produces two genetically identical daughter cells. Meiosis produces haploid cells, mitosis produces diploid cells
What is found in the nucleus of eukaryotic cells?
Chromosomes which are long coiled up molecules of DNA
What takes place in sexual reproduction?
At fertilisation the male gamete fuses with the female gamete to form a fertilised egg known as a zygote which is diploid. The zygote then undergoes cell division by mitosis and develops into an embryo ( which inherits characteristics from both parents as it has a mixture of chromosomes).
Descrbe what happens in meiosis
Before the cell divides it duplicates DNA so there is enough for the new cell. In the first division the chromosomes line up in pairs in the centre in a pair there is both a mother and father chromosome. The pairs are pulled apart. In the second division the chromosomes line up at the centre and the chromatids are pulled apart. You get four genetically different haploid daughter cells which are gametes as they have a single set of chromosomes.
Define mutations
Mutations are rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome
