Biology #5 Flashcards
Disadvantage of asexual reproduction
- offspring all genetically identical
- no genetic variation
Define asexual reproduction
as a process resulting in the production of genetically identical offspring from one parent
Advantage of asexual reproduction
- faster reproduction
- requires less energy
What type of organisms can produce asexually
Mainly bacteria, fungi, small plants/animals, potatoes and bulbs
Define sexual reproduction
as a process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other
Gametes
Gametes are formed by meiosis, a type of cell division which produces cells with half the chromosome number
Advantage of genetic variation in the wild
Genetic variation means that organisms can better survive changes to the environment. Some individuals may die, but as the population is genetically diverse some will have the traits to survive
Vantages of genetic variation in crops
Having crop plants that are genetically different is important for ensuring the crop can survive environmental change
Male part of a flower
Stamen - consists of filament (long, thin) and anther (pollen)
Female part of a flower
Carpel – consists of stigma (sticky
opening), style (long tube connecting stigma to ovary), ovary (houses ovules; becomes fruit), and ovules (develops female gametes; become seeds)
Define pollination
As the transfer of pollen grains from an anther to a stigma
Define self pollination
As the transfer of pollen grains from the anther of a flower to the stigma of the same flower or a different flower on the same plant
Cross pollination
As the transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
Define STI
As an infection that is transmitted through sexual contact
HIV
- HIV is a pathogen that causes an STI
- HIV infection may lead to AIDS
Different ways HIV is transmitted
- unprotected sex
- organ transplant
- blood transfusion
- pregnancy breastfeeding
- use of non sterile syringes and tools
Ways to reduce the spread of HIV and other STI’s
- use a condom during sex
- avoid breastfeeding if you are HIV positive
- don’t share needles for injecting drugs
-make sure you check if someone has an STI before sex
FSH
- stimulates egg maturation in the follicles of the ovary
- stimulates follicles in the ovaries to secrete oestrogen
LH
- At its peak stimulates ovulation (release of egg into oviduct)
- results in the formation of a corpus luteum
Oestrogen
- stimulates the uterus to develop a lining (to replace the lining lost during menstruation)
- post ovulation, inhibits FSH and LH production in the pituitary gland
Progesterone
- maintains and thickens lining of the uterus
- inhibits FSH and LH production
- if fertilisation doesn’t occur, levels drop and menstruation occurs
Define inheritance
The transmission of genetic information from generation to generation
DNA
Chromosomes are made of DNA which contains genetic information in the form of genes
Genes
As a length of DNA that codes for a protein
Define allele
as an alternative form of a gene
Diploid
99.9% of the cells in your body
contain two copies of each
chromosome. These cells are
known as diploid cells.
Haploid
The only cells with one copy of
each chromosome are sex cells
(sperm, eggs, pollen). These are
known as haploid cells.
DNA expession
All our cells contain the same genes,
the only difference between them is
which genes they express (i.e. produce
proteins from)
Variations of genes - alleles
Most genes will have multiple
variations between people in their
sequence. These are known as Alleles.
Everyone has two alleles for each gene,
one on each chromosome.
The central dogma of biology - dna to rna to protein
Once we transcribe our DNA into mRNA it is sent to ribosomes in the cytoplasm
- Ribosomes read the sequence of
nitrogenous bases and translate it into a
specific sequence of amino acids, forming a protein
- 3 bases = 1 codon = code for 1 amino acid
Seed requirements for germination
Germination = a seed sprouting
* Germination requires 3 factors:
Water (needed to soften seed)
Suitable temperatures (makes sure
it is the right time of year to sprout)
Oxygen (needed for respiration to
produce energy for cell division)
How proteins are made
DNA always remains in the nucleus
* DNA is copied to form mRNA (messenger RNA) in the nucleus
Ribosomes convert the genetic sequences into a chain of amino
acids which folds to form a protein
Mitosis
Cell division giving rise to genetically identical cells
* Used for growth, repair, replacing cells and asexual reproduction
* During mitosis the DNA/ chromosomes replicate (makes a copy of itself), then the cell divides
* Half the chromosomes will move into each divided cell, creating two Daughter cells with the same chromosome as the original parent cell
Meiosis
Used for making sex cells /
gametes. Only occurs in testes in
males and ovaries in females
* Produces 4 haploid daughter cells
with half the chromosome number
of a regular body cell
* This is because at fertilisation the
two haploid gametes will fuse,
making the zygote diploid
Stem cells
- Unspecialised cells that can divide by
mitosis to become specialised cells
Co dominance
Both alleles in a heterozygous organism
are expressed in equal parts on the
organism
The alleles do not blend, but are both
expressed at the same time
Multiple allele traits
Involves genes that have more than
two different alleles
* Possible blood types: A, B, AB or O
* Order of dominance:
IA is equal dominance to IB (an example of
codominance)
IA and IB are dominant over IO
Linked traits
- Traits that are “linked” are
found on the same
chromosome. This means
they tend to be inherited
together more frequently
than by random chance
Sex linked traits
Sex linked traits is where the gene for a specific phenotype is located on a sex chromosome
* Males are much more likely to express a recessive phenotype for sex length traits e.g. pattern boldness green – red colour blindness
