B13 Reproduction Flashcards
What is sexual reproduction
Where male and female gametes join ( fuse ) together to create an offspring which is genetically different to either parent
What are the gametes for animals and plants
Animals: sperm (M) and egg cell (F)
Plants: pollen (M) and egg cell (F)
What is the process by which gametes are produced
Meiosis
What is asexual reproduction
There is only one parent and no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offsprings are genetically identical to the parents ( clones ). Only mitosis is involved
How many chromosomes do gametes have and why
They only have one copy of each chromosome ( 23 chromosomes ) because when gamete fusion takes place, you get the right amount of chromosomes again ( 46 )
1 example of cells that divide by meiosis
Cells in the reproductive organs ( testes and ovaries ) divide by meiosis to form gametes
What happens when a cell divides to form gametes
Copies of genetic information are made
The cell divides twice to form 4 gametes, each with a single set of chromosomes
All gametes are genetically different from eachother
What happens to gametes at fertilisation
Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo devlops the cells differentiate
Advantages of sexual reproduction ( SKIP NOT NEEDED )
Offsprings have a mixture of 2 sets of chromosomes which provides variation
Variation increases chance species of surviving a change in environment as some variations have traits that allow them to survive ( others will die through natural selection )
These variations will breed and allow the species to adapt and evolve in the new environment
We can use selective breeding to create better variations of animals and speed up natural selection
Advantages of asexual reproduction ( SKIP NOT NEEDED )
There only needs to be one parent
Asexual reproduction uses less energy because organisms don’t have to find a mate
Asexual reproduction is faster than sexual
Many identical offspring can be produced in favourable conditions
How do malarial parasites have the best of both worlds ( SKIP NOT NEEDED )
Malarial parasites reproduce asexually in the human host but sexually in the mosquito
How do fungi have the best of both worlds ( SKIP NOT NEEDED )
Many fungi reproduce asexually by spores but also reproduce sexually to give variation
How do plants have the best of both worlds ( SKIP NOT NEEDED )
Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
What is DNA and what is it’s structure
The genetic material in the nucleus of a cell is composed of a chemical called DNA. DNA is a polymer made up of two strands forming a double helix. The DNA is contained in structures called chromosomes.
The DNA polymer is made up of repeating nucleotide units
What is a gene
A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
What is a genome and what is the significance of the human genome
The genome of an organism is the entire genetic material of that organism. The whole human genome has now been studied and this will have great importance for medicine in the future.
What are the benefits of understanding the human genome
Search for genes linked to different types of disease
Understanding and treatment of inherited disorders
Use in tracing human migration patterns from the past.
What is the structure of DNA
DNA is a polymer made from four different nucleotides. Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar
What are the 4 bases of DNA
A, C, G, T
C and G are complementary
A and T are complementary
How the bases of DNA code for particular amino acids
A sequence of three bases is the code for a particular amino acid. The order of bases controls the order in which amino acids are assembled to produce a particular protein.
What do the strands of DNA consist off
The long strands of DNA consist of alternating sugar and phosphate sections. Attached to each sugar is one of the four bases.
Where are proteins made in a cell
They are made in structures called ribosomes in the cytoplasm by protein synthesis
What can the proteins made in protein synthesis go on to do
Enzymes: amylase
Hormones: insulin
Structural proteins: collagen
What is the process of protein synthesis
Transcription:
mRNA unzips the DNA strand and makes a copy of the code using complementary bases called a template
Translation:
The template is the right size to move out of the nucleus to the ribosome
Carrier molecules bring the correct amino acid to each combination of triplet bases on the template
The amino acids then bond together to form a specific protein using that specific combination of amino acids
The bonded amino acids fold into the right shape to make a protein and the specifc shape allows it to perform it’s function
How do mutations occur and what are the effects
Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.
A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
How does DNA effect genes’ expressions
Not all parts of DNA code for proteins. Non-coding parts of DNA can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed
Homozygous
homozygous: an individual with two identical alleles for a characteristics e.g: BB,bb
Heterozygous
heterozygous: person with different alleles for a characteristic e.g: Bb
Gamete
A sex cell
Chromosome
A strand of DNA
Gene simple definition
A section of DNA
Allele
A section of a gene
Genotype
Describes the genetic makeup or alleles present in an individual regarding their characteristics
Phenotype
Describes the physical apearance of an individual regarding their characteristics
Dominant
An allele that there only needs to be 1 of in order for the trait to be shown
Recessive
An allele that there must be 2 of in order for the trait to be shown
What is ploydactyly and what is it caused by
Polydactyly (having extra fingers or toes) is caused by a dominant allele.
What is cystic fibrosis and what is it caused by
Cystic fibrosis (a disorder of cell membranes) is caused by a recessive allele.
What are the positives about embryonic screening
Positives:
It will help stop people suffering
Treating disorders costs the government and tax payers a lot of money so reducing the number of people with the disease will save money
There are laws to stop it going too far. At the moment parents cannot even select the sex of their baby ( unless for health reasons )
What are the negatives anout embryonic screening
It implies that people with genetic problems are ‘undesirable’ - this could increase prejudice
There may come where everyone wants to screen their embryos so they can pick the most desirable one
Expensive
What is the male and female sex chromosomes ( SKIP NOT NEEDED )
Male: XY
Female: XX
