B13- Reproduction Flashcards
2 types of reproduction
Asexual and sexual
Asexual
Parent?
Division?
Genetic material?
Variation?
Examples?
One parent
Mitosis
No mixing of genetic information (clones)
No variation
Fungi, bacteria, starfish
Sexual
Parent?
Division?
Genetic material?
Variation?
Examples of cells?
Male and female gametes fuse together to form a zygote
Meiosis
Inherit genetic information from both parents
More variation
Animals, sperm and egg cell. Plants, pollen and egg cells
Meiosis
Forms?
3 steps?
Gametes (haploid cells)
1. Parent cell has 46 chromosomes (2 sets)
2. Genetic info is copied so there are 92 chromosomes (4 sets)
3. Cell quickly divides twice, forming 4 gametes each with 23 chromosomes (1 set)
Diploid cell chromosomes?
Haploid cell chromosomes?
46 chromosomes
23 chromosomes
How is variation achieved in meiosis?
Each gamete is genetically different. When the gametes fuse, a set of chromosomes comes from each parent. The genes in the new zygote will contain different forms of the alleles (genes) from each parent.
Asexual reprod
Ads & dis?
Ads- time and energy efficient as no mates required. Quickly produces large no of offspring
Dis- limited variation, if one can’t survive, none can
Sexual reprod
Ads & dis?
Ads- produces variation, better for natural selection. Used by humans for selective breeding for food production
Dis- takes time and energy to find mates. Slower than asexual
Reproduction in fungi
Most common type?
How are both types used?
Asexual
Asexual= produces spores by mitosis, stable conditions
Sexual= poor conditions, forms haploid spores with variation
Reproduction in plants
How are both types used?
Asexual= plant grows due to mitosis, e.g strawberry runners and bulbs
Sexual= pollen from one flower reaches another by animals and insects, pollen fuses w egg cell
Reproduction in malaria parasites
How are both types used?
Asexual= when inside human liver and blood cells
Sexual= when inside female mosquitos due to a temp change when the mosquito bites a human
What is a genome?
What was the project called and what did it involve?
When did it happen?
An organism’s entire set of genetic material
The Human Genome Project-> when the entire human genome was mapped out and sequenced
from 1990 to 2003
Structure of DNA
A polymer made up of repeating nucleotides to form a double helix shape
Advantages of the human genome project?
-Understand inherited disorders
-Understand human evolution and history
-Understand relationships between organisms
What is a gene and what does it do and why?
A small section of DNA
Codes for a sequence of amino acids
In order to make a specific protein
What is a nucleotide made up of?
What are the 4 bases?
What is each base attached to?
A sugar, a base and a phosphate
A T C G
Each attached to a sugar
What groups are nucleotides in?
What is needed to code for one amino acid?
What changes the type of protein made?
Nucleotides are grouped in 3
3 bases code for 1 amino acid
The order of bases
What bases are always together?
C and G
A and T
RNA
What is it?
Key feature?
Base changes?
A copy of DNA
Single stranded
U instead of T
U pairs with A
2 stages of protein synthesis
- Copying the DNA
- Making the protein, leaves nucleus goes to ribosome
Protein synthesis
How is DNA copied in protein synthesis?
How is the protein made?
DNA’s double helix unzips. RNA is made and leaves the nucleus.
RNA leaves nucleus, binds to ribosome. Cytoplasm has ‘carrier molecules’ that bind to RNA and bring specific amino acids until the protein is formed. Once chain is complete, the protein detaches from carrier molecules and folds up, carrier molecules detach from RNA.
Mutations def?
Random changes that can occur in an organism’s DNA
Phenotype
Physical appearance an organism expresses
How many alleles in a gene?
Where does each come from?
Key fact?
2
One from mum, one from dad
Only expresses one
Genotype
The alleles present in someones genetic material
Homozygous
Two of the same alleles for a characteristic
Heterozygous
Two different alleles for a characteristic
Dominant allele def?
How is it shown?
An allele that overrides other alleles, will always be expressed if it is present. Capital letter
Recessive allele def?
How is it shown?
An allele that doesn’t override other alleles, only expressed if both are recessive. Lower case letter
How to predict the outcome of offsprings genetics?
Punnett squares. One parent on top, one on side. Match together in four boxes, can work out percentages and ratios
Carrier
An allele in a genotype but not expressed in phenotype
Human female sex chromosome pair?
Human male sex chromosome pair?
XX
XY
Chance of boy or girl using punnett square
50%
X Y
X XX XY
X XX XY
Polydactyly
Causes?
Caused by?
Allele pairs that have condition?
Extra fingers or toes
Dominant allele
Pp, PP
Huntington’s disease
Causes?
Caused by?
Problems with nervous system, leads to death
Dominant allele
Cystic fibrosis
Body parts it affects?
Causes?
Caused by?
Allele pairs that have condition?
Lungs, digestive system, reproductive system
Thick, sticky mucus which clogs up organs like pancreas, stops it secreting enzymes.
Two recessive alleles
ff
Way to cure genetic disorders?
Genetic engineering by replacing faulty alleles with healthy ones
How to tell if a baby will have a genetic disorder?
Screening of embryonic and fetal cells for the alleles that cause them
3 Arguments for embryonic screening?
Are they economic, social or ethical?
Reduces number of people suffering from disorders- Ethical
Reduces NHS’s expenses on providing healthcare- Economical
Regulations prevent it getting out of hand- Social
5 Arguments against embryonic screening?
Are they economical, social or ethical?
-Could pick desirable characteristics- Ethical
-Embryo doesn’t have a choice- Ethical
-Expensive- Economical
-False positive results can end healthy lives- Social
-Extracting cells can cause a miscarriage- Social
