Reproduction Flashcards
Haploid cells
Contain just 23 chromosomes
Sexual reproduction
Male and female sex cell Gametes fuse -> zygote Meiosis Inherit genes from both parents and characteristics Won’t be identical
Asexual reproduction
1 parent Mitosis No fusion of sex cells No mixing of genetic information No variation Genetic material identical to parent
Diploid cells
Contain 23 pairs of chromosomes
Gametes
Sex cells
Haploid cells
Sperm and egg
Fertilisation
Egg and sperm cell = 23 chromosomes
Fuse to form 46 chromosomes -> 23 pairs
Fertilisation complete = new cell divides by mitosis, number of cells increase, cells differentiate
Meiosis process
1) Each chromosome is duplicated forming X-shaped chromosomes (46 from parent cells)
2) First division = chromosome pairs line up down the centre of the cell, pulled apart -> each new cell has one copy of each chromosome
3) Second division = chromosomes line up along centre of the cell with 23 pairs on each side and the arms of the chromosomes are pulled apart
4) Four haploid daughter cells produced = gametes
Reproduction in fungi
Asexual
Moulds rot our food and reproduce asexually
Fungal spores produced by mitosis
Two hyphae join and nuclei fuse = hypha has 2 sets of chromosomes
Undergoes meiosis = haploid spores, each with 1 set of chromosomes
Spores may produce fungi better adapted to survive the adverse conditions
Sexual Reproduction in plants
Gametes = pollen and egg produces using meiosis
Pollen reaches female parts of another flower = pollination
Once gametes fuse = seeds form
Introduces variation
How are flowers adapted in reproduction?
Adapted to attract animal pollinators (insects, birds or bats)
To carry pollen to another flower
Asexual reproduction in plants
New plants are formed even if flowers are destroyed by frost, eaten or fail to be pollinated
Disadvantage = new plants identical to parents = no variation
Reproduction in malaria parasites
Asexual and sexual
Asexually in human liver and blood cells
Drop in temperature
Mosquito triggers sexual reproduction inside red blood cells
Sexual forms develop, burst out of the blood cells forms zygote with 2 sets of chromosomes
Zygotes undergo meiosis = produce asexual parasites
What is DNA?
A polymer
What are genes?
Small sections of your DNA
Determines inherited characteristics
Codes for sequence of amino acids to make a specific protein
What do enzymes control in your DNA
Control your cell chemistry
What is a genome?
Entire genetic material of the organism
How does mitochondria affect our DNA?
Contain their own DNA
Inherit your mitochondrial DNA from your mother because it comes from the mitochondria in egg
What does understanding genomes help people with?
Understanding inherited disorders
See peoples increased risk of developing many diseases
Predict risk for each individual = make lifestyle choices to help reduce the risk
Choosing the best treatment for a patient
Evolution and history
What bases in the DNA always join together?
A and T
C and G
What do the long strands of DNA consist of
Alternating sugar and phosphate sections
Attached to each sugar is a base
What is a nucleotide?
Each unit of a sugar, phosphate and base
How to make a protein
1) Template leaves nucleus and binds to surface of ribosome
2) Cytoplasm contains carrier molecules
3) Carrier molecules attach to the template of a specific amino acid
4) Amino acids join to form protein
5) Carrier molecules bring amino acids to add to protein chain
6) Protein detaches from carrier molecules
7) Carrier molecules detach from template and return to cytoplasm to bring more amino acids
8) Once protein shape is complete the molecules fold to form a unique shape to carry out its functions in the cell
What happens if you change the order of the bases?
Alter the template resulting in a different sequence of amino acids
Changing the protein synthesised by the gene
Describe the structure of a nucleotide?
A phosphate is attached to a sugar
Which consists of 4 bases
Which are A,C,T and G
What do non-coding parts of the DNA do?
Switch genes on and off
Explain how we can synthesise so many different chemicals with so few genes
Affect how genes are expressed
Affects the phenotype (physical appearance)
How is a mutation formed
When new genes form changes in existing genes
Mistakes made in copying the DNA for new cells as they reproduce
What do some mutations code for?
Change in the amino acids alter protein folds to give a different shape
Active site of enzyme can no longer fit the substrate, loses its strength
What is an allele
Each of 2 or more alternative forms of a gene that arise by mutation, found at the same place on a chromosome
Homozygote
2 identical alleles
Heterozygote
Different alleles
Genotype
Describes alleles present or genetic makeup of an individual
Phenotype
Physical appearance
Where does a genotype work
At the level of the DNA molecules to control the proteins made
What information does a punnet square give us
Alleles for a characteristic carried by parents
Possible gametes that can be formed
How gametes may combine to form characteristic in their offspring
What is Polydactyly
Born with extra fingers or toes
How does someone get Polydactyly
Inherited from 1 parent
50% chance of passing disorder on = half your gametes will contain the faulty dominant allele
What does cystic fibrosis affect?
Organs of the body
What is cystic fibrosis?
Cell membranes prevent the movement of certain substances from one side to the other
What happens as a result of cystic fibrosis
Mucus made by cells becomes very thick and sticky
Organs are clogged up = stop working properly
Pancreas cannot secrete enzymes = tubes which enzymes are released is blocked
Most are infertile
Treatments for cystic fibrosis
No cure
Physiotherapy = clear lungs
Antibiotics = replace enzymes in pancreas that cannot be produced
What is cystic fibrosis caused by?
Recessive allele inherited by both parents
1/25 have allele
Most are unaware they have it
Curing genetic disorders
No cures
Very serious and short lives
Genetic engineering = looking at replacing faulty alleles with health ones and gene replacement
What is an amniocentesis test
Taking fluid from around foetus used for genetic screening
What is chorionic villus
Sample of tissue for placenta
Using fetal cells to genetically screen foetus
Carrying out screening
DNA isolated form embryo cells and tested for specific disorders
Concerns about embryo screening
-Increase risk of miscarriage
+becoming more reliable and accurate
-can give false positive or negative test results
-have to make decision to keep or terminate pregnancy = science cannot help
-expensive
-risk to a demand character (people wants certain sex or intelligence)
