B13 - Reproduction Flashcards
what does sexual reproduciton involve
involves the joining of male and female gametes
- sperm and egg cells in animals
- pollen and eggs cells in folwering plants
what does the formation of gametes involve
a type of cell division called meiosis
what is sexual reproduction
there is mixing of genetic information which leads to variety in the offspring
what is asexual reproduction
involves only one parents and no fusion of gametes, there is no mixing of genetic information so this leads to genetically identical offspring (clones)
what does meiosis produce
gametes that have half the normal chromosone number, and so when fertilisation happens, the cell that is produced (zygote) has the full number of chromosones again
where in humans does meiosis occur
in the reproductive organs (ovaries and testies)
what happens during meiosis
- copies of the genetic information are made
- the cell divides twice to form four gametes, each with a single set of chromosones
- all gametes are genetically different from each other
what happens after fertilisation
the cell thats created divides by mitosis over and over again to produce lots of new cells wich differenciate as the embryos develops
how is DNA found
in long structures called chromosones
what does DNA make up
all of genetic materials in cells, and thats its found in the nuclues
what is the structure of DNA
double helix structure
what is a gene
a small section of DNA on a chromosone, and that each gene codes for a particular sequence of amino acids which are put together to make a spersific protein
what is a genome
the entire genetic material of that organism
why is scientists studying the human genome is important
- scientists can search for genes linked to different types of disease
- scientists can undertand and treat inherited disorders
- scientists can trace migration patterns from the past
what is a gamete
reproductive cells
what is an allele
different versions of the same genes
what is a dominat allele
an allele that is always expressed unless the allele is homozgyous
what is homozygous
2 of the same alleles
what is heterozygous
2 different alleles
what is a genotype
the combination of alleles (forms of the gene) that a person has for a particular trait
what is a phenotype
The observable characteristics of an organism (seen just by looking - like eye colour, or found – like blood type
what are most characteristics a result of
multiple genes interacting rather than a single gene
how are some disorders are inherited
inheritence of certain of alleles
what is polydactyly
having extra toes and fingers, caused inhertance of dominant alleles
what is cystic fibrosis
a disorder of cell memebranes, inherited disorder by a recessive alleles
what are some economic, social and ethical judgements for embryo screening
eco:
- expensive, cant be offered to everyone
soc and eth:
-The probability of the couple having a child with a genetic disorder.
- Termination of the pregnancy.
- Therapeutic treatments possible for the child.
- Financial implications of having the child.
- Effect on existing siblings.
- Ethical issues.
how many chromosones pairs are there for a normal human
23 pairs 46 single
how many chromosones pairs control charcteristics
22 pairs, one of pairs determines sex
