Bio Chp 1 and 2 key words Flashcards
define inheritance
the transmission of traits from one generation of organism to the next
define genetics
the science of heredity and heredity variation
define genes
segments of DNA that codes for a particular characteristics
define gene locus
gene locus is where a gene is located on a specific chromosome
define alleles
alleles are the alternate form of the same genes. They occupy the same positions on a pair oof homologous chromosomes
define homologous chromsosmes
they are a pair of chromosomes that have the same shape, size and the same sequence of genes. One chromosome is inherited from the male parent and the other from the female parent.
define karyotype
appearance of a complete set of chromosomes
define phenotype and genotype
phenotype - the expressed trait or characteristic of an organism that arises from its corresponding genotype
genotype - the genetic makeup or combination of alleles for a particular gene
define homozygous and heterozygous
homozygous - in a pair of homologous chromosome, homozygous refers to having 2 identical alleles of a particular gene
heterozygous - having 2 diff allele of a particular gene
define chromosome no.
no. of chromosome in a cell. it is fixed for each species.
define ploidy
no. of sets of chromosomes present in an organism
define haploid
haploid - describe the condition in which nucleus of a cell has 1 complete set of chromsome
why are there usually 2 alleles in the genotype of an organism
this is coz each allele is contributed by each parent when the male and female gamete fuse together during fertilisation. each gamete carries one set of chromosome, haploid, and fuse to give a diploid organism
purpose of test cross and why its conducted
A test cross is used to determine the genotype of an organism showing the dominant trait (as it can be homozygous or heterozygous for the trait);
The organism is crossed with another organism that is homozygous recessive for the trait and the phenotypes of the offspring are observed;
explain hwo the results of a test cross can be interpreted
If all offspring show the dominant trait, the organism is homozygous dominant for the trait;
If half of the offspring show the dominant trait and the other half show the recessive trait, the organism is heterozygous for the trait;
define codominance
In codominance, both alleles express themselves in the heterozygote, which express a phenotype intermediate between that of its pure-pred parents.
outline sex determination in humans
females have 2 X chromsomes. Males have one X and one Y chromsome
distinguish between structure of human X and Y chromsome
- X is larger then Y
- X carries more genes that Y
Distinguish between sex chromosomes and autosomes in humans.
- Sex chromosomes determine sex but autosomes codes for the proteins needed for other body functions
- There is 1 pair of sex chromosome but 22 pairs of autosomes in humans;
- Males and females have different pairs of sex chromosome (XY and XX) but the same types of autosomes;
define asexual reproduction
Asexual reproduction is the process genetically identical offspring are produced from one parent, without the fusion of gametes.
define gametes
gamete is a reproductive cell of an organism. Female gametes are named ova or egg cells, and male gametes are called sperms.
define mitosis
Mitosis is a type of cell division that gives rise to genetically identical cells. The chromosome number of the genetically identical daughter cells remains the same after the division.
Prophase
DNA condenses into chromosomes to become more visible. The membrane around the nucleus disappears.
Metaphase
Chromosomes line up randomly in the equator of the cell.
Anaphase
Sister chromatids are pulled to different ends of the cell , each become a new chromosome.
Telophase
Nuclear membranes form around the chromosomes at each end of the cell.
what happens during the interphase of mitosis
interphase occurs to prepare for cell division. Cell growth and DNA replication occurs during interphase.
gimme AD for asexual repduction
A:
1. only 1 parent required - happens fast
2. no fusion of gametes
3. all beneficial qualities from parent is passed down to the offspring
D:
Lack of genetic variation makes the species not well adapted to the environment.
why is mitosis important?
- allows for asexual reproduction to occur
- mitosis produces new cells, allowing for multi cellular organisms to grow
- replaces dead or damaged cells
sexual reproduction
Sexual reproduction is the process that involves the fusion of two gametes to form a zygote (fertilised egg). It produces genetically non-identical offspring.
meiosis
Meiosis is a reduction division that gives rise to genetically non-identical daughter cells. The chromosome number is halved due to the separation of homologous chromosomes. it is used to produce gametes
Why is meiosis important?
- Maintaining the diploid number in zygotes genetic stability;
- Meiosis produces haploid gametes and hence, when the nucleus of a male gamete and female gamete fuse to form a zygote and the normal diploid number is restored in zygotes;
- Better adaptation to changes in the environment since meiosis results in genetically dissimilar offsprings
what esnures genetic stability in offsprings during SR?
the offspring that develops from the zygote would have the same chromosome number as the parents.
This ensures genetic stability throughout the generations of the same species.
AD of sexual reprdoction
A:
1. Genetic variation in offspring, making them Better adapted to the environment and environmental changes
2. Colonise new areas by seed dispersal
3. Inherit beneficial qualities from both parents
D:
1. 2 parents are required
2. fusion of gametes required
3. longer process than AR
