4.6.1 Reproduction (will come up) P2 Flashcards
What is sexual reproduction
Type of reproduction
Involves the production of gametes by meiosis
A gamete from each parent fuses to form a zygote
Genetic information from each gamete is mixed so the resulting zygote is unique
What are gametes
Sex cells (sperm + egg, pollen + egg) Haploid cells (half the number of chromosomes)
What is meiosis
Form of cell division involved in the formation of gametes in reproductive organs
Chromosome number is halved
Involves 2 divisions
What must occur prior to meiosis
Interphase - copies of genetic information are made during this process
What happens during the first stage of meiosis
Chromosome pairs line up along the cell equator
The pair of chromosomes are separated and move to opposite poles of the cell
Chromosome number is halved
What happens during the second stage of meiosis
Chromosomes line up along the centre of cell
The chromatids are separated and move to opposite poles of the cell
Four unique haploid gametes are produced
Why is meiosis important for sexual reproduction
It increases genetic variation
It ensures that the zygote formed at fertilisation is diploid
Describe fertilisation and its resulting outcome
Gametes join together to restore the normal number of chromosomes and the new cell then divides by mitosis
As the embryo develops, cells differentiate
What is asexual reproduction
Involved mitosis only
Produces genetically identical daughter cells
Asexual reproduction involves only one parent and no fusion of gametes.
What is DNA
A double-stranded polymer of nucleotides, wound to form a double helix
Define genome
The entire genetic material of an organism
Why is understanding the human genome important
Important for the development of medicine in the future
Searching for genes linked to different types of disease
Understanding and treating inherited disorders
Tracing human migration patterns from the past
What is a chromosome
A long, coiled molecule of DNA that carries genetic information in the form of genes
How many chromosomes do human body cells have
46 (23 pairs)
How many chromosomes do human gametes have
23 chromosomes
Define gene
A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
What are the monomers of DNA
Nucleotides
What are DNA nucleotides made up off
Sugar
Phosphate
1 of the 4 bases
State the full names of the four bases found in nucleotides
Adenine Thymine
Cytosine Guanine
How nucleotides interact to form a molecule of DNA
Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand
Base connected to each sugar
Complementary base pairs (AT, CG) joined by weak hydrogen bonds
How a gene codes for a protein
A sequence of 3 bases in a gene forms a triplet
Each triplet codes for an amino acid
The order of amino acids determines the structure and function of protein formed
Why is the ‘folding’ of amino acids important in proteins such as enzymes
The folding determines the shape of the active site which must be highly specific to the shape of its substrate
What is protein synthesis
The formation of a protein from a gene
What are the 2 stages of protein synthesis
Transcription
Translation
What does transcription involve
The formation of mRNA from a DNA template
Outline transcription
- DNA double helix unwinds
- RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand
- RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand
- mRNA formation complete. mRNA detaches and leaves the nucleus
What does translation involve
A ribosome joins amino acids in a specific order dictated by mRNA to form a protein
Outline translation
- mRNA attaches to a ribosome
- ribosome reads the mRNA bases in triplets. Each triplet codes for 1 amino acid which is brought to the ribosome by a tRNA molecule
- A polypeptide chain is formed from the sequence of amino acids which join together
