B13 Flashcards
Sexual reproduction is
Where genetic info from two organisms is combined to produce offspring which are genetically different to either parent
A gamete is
A sperm or egg or pollen
In humans, each gamete contains
23 chromosomes
The egg and the sperm cell fuse together to form
A cell with the full number of chromosomes (46)
Definition or SEXUAL REPRODUCTION
SEXUAL REPRODUCTIONS involves the fusion of make and female GAMETES. because there are TWO parents, the offspring contain a MIXTURE OF THEIR PARENT’S genes
Fertilisation
SPERM AND EGG guves OFFSPRING (fertilised egg)
Why dies the offspring inherit features from both parents
Uts recieved a mixture of chromosomes from its mum and dad
The mixture of genetic material produces
Variations in offsprings
ASEXUAL REPRODUCTION DEFINTION:
In ASEXUAL REPRODUCTION there’s only ONE parent. there’s NO FUSION of gametes, NO MIXING of chromosomes and NO GENETIC VARIATION between parent/offspring. Offspring is GENETICALLY INDENTICAL to the parent
Advantages of SEXUAL REPRODUCTION?:
-produces variation in the offspring
-if the environment changes variation gives a survival advantage by natural selection
-natural selection can be speeded up by humans in selective breeding to increase food production.
Advantages of asexual reproduction
-only one parent needed
-more time and energy efficient as do not need to find a mate
-faster than sexual reproduction
-many identical offspring can be produced when conditions are favourable
DNA is a
polymer that is made up of four different nucleotides. Two strands twist together to form a double helix.
Each nucleotide is made of
a sugar and phosphate group with one of four different bases attached.
The four bases are
A, C, G and T
Complementary base pairing is
A always pairs up with T and C always pairs up with G
- the order of bases in a gene that decides the order of amino acids in a protein
Whats a template
Template is Made of the part of the DNa that codes for a specific protein. Each protein will have a different template
Explain insertions
Insertions are where a new base is inserted into the DNA where it shouldn’t be.
Insertions changes the way the three groups of bases are read, changes the amino acids they code for.
This can cause a knock on affect for the bases further down the line as they cancchange more than one amino acid
Deletions explained
Its when a random base is deleted from the DNa base sequence.
They change theway that the base sequence is read and have knock on effects further down sequence
Substitutions explained
When a random base in the DNA base sequence is changed to a different base
Dominant alleles
Are always expressed even uf only one of the allekes is dominant
Recessive alleles
Are only expressed if there are 2 recessive alleles
There are — chromosomes in the human body
23 pairs (46)
Of these 23 pairs ____ are matched paris of chromosomes that just control characteristics. The ____ pair are labelled ___ or _____. They decide your sex
22, 23rd, XY or XX
Homozygote
An individual with two identical alleles for a characteristic (BB or bb)
Heterozygote
An individual with different alleles for a characteristic
Why do sex cells have half the usual number of chromosomes
Cause each egg and sperm have 23 chromosomes
Allele
Different form of a gene
Genotype
Describes the alleles present or genetic makeup of an individual regarding a particular characterisitic (Bb or bb)
Phenotype
Describes the physical appearance of an individual regarding a particular charscreristics, (black fur or brown fur)
Gametes
Egg or sperm cell
Carrier
Someone who carries the faulty gene but its recessive (heterozygous)
During in vitro fertilisation (IVF), embryos are fertilised in a laboratory, then implanted into the mother’s womb, before it’s implanted, it’s possible to remove a cell from each embryo and analyse its genes. This way….
Many genetic disorders can be detected in this way, such as cystic fibrosis. Also possibke to get DNA from an embryo in the womb and test that for disorders.
For embryos produced by IVF - after screening..
Embryos with ‘bad’ alleles would be destroyed
For embryos in the womb - screening could lead
to the decision to terminate the pregnancy
Against Embryonic Screening
- it implies that people with genetic problems are not wanted - leads to prejudice.
- may come a point where everyone wants screening so they can pick a desirable one
- expensive
For Embryonic Screening
- will help to stop people suffering
- treating disorders costs gov MONEY
- there are LAWS to stop it going too far.
- atm parents cannot even select the sex of their baby.
IVF explained
- involves collecting eggs from the woman’s ovaries and fertilising them in a lab using the man’s sperm
- involves intra-cytoplasmic sperm injection (ICSI), sperm injected directly into egg.
- fertilised eggs are grown into embryos in a lab incubator.
- once embryos are tiny balls of cells, one or two of them are transferred to the woman’s uterus to improve the chance of pregnancy
- FSH/LH guven before egg collection to stimulate several eggs to mature
Fertility treatment pros/cons
Pros:
- gives an infertile couple a child - a pretty obvious benefit
CONS:
- multiple births can happen (high rist of stillbirth…)
- success rate low - process stressful (physically/mentally)
-
Against IVF
Results in unused embryos that are enventually destroyed.
- some people think its unethical - potential human life each embryo
- genetic testing of embyos implantation also raises ethicak issues as some people think it coukd lwas to the selection of preferred characterisitcs.
