Chapter 9 Glossary terms Flashcards
Gonads
Organs that produce gametes
Ovaries
Organ in females that produce eggs, ova
Testes
Organ in males that produces sperm
Gametes
Egg, sperm - haploid cells which fuse during fertilisation in organisms that reproduce sexually
Zygote
first diploid cell formed after the fusion of two gametes
Fertilisation
Fusion of a male and female gamete
Germline cells
Specialised diploid cells found in the gonads that can undergo meiosis
Somatic cells
Diploid body cells. All body cells except gametes
Diploid cells
Cells with two sets of chromosomes (2n), one set derived from each parent. In humans the diploid number is 46
Haploid cells
Cells with one set of chromosomes (n). These cells are produced by meiosis. In humans the haploid number is 23
Gene
A section of DNA that codes for a protein, basic unit of heredity.
Allele
Alternative form of a gene
Genome
Al of the genes in a cell. Not all genes are switched on in any cell, but all genes are present. Every cell has the same genome.
Chromosome
Threadlike structures made up of DNA and protein. Only visible during cell division.
Chromatin
Chromosomes when not in mitosis or meiosis. Chromatin are made up of DNA and protein
Autosome
Any chromosome other than sex chromosomes. Humans have 44 autosomes
Sex chromosomes
Chromosomes that determine gender. In humans there are 2 sex chromosomes. Female: XX Male: XY
Homologous pairs of chromosomes
Chromosomes that are matched, one set derived from the mother and the other from the father. Important for successful meiosis producing viable gametes. Each pair carry genes controlling the same trait.
Chromatid
A copy of a duplicated chromosome, joined to the other copy by the centromere. Required for cell division and is produced in the S phase of the cell cycle.
Karyotype
a diagram of the chromosomes, arranged in order of size, position of the centromere, and sex chromosomes displayed together.
Binary Fission
Bacterial (proaryotic) cell division where one cell divides into 2 identical daughter cells
Mitosis
Cell division for growth and repair of eukaryotic cells where one diploid cell divides into 2 genetically identical daughter cells
Meiosis
Cell division for the production of gametes, where one specialised diploid cell can produce 4 genetically different haploid cells.
Interphase
cell replication. the chromatids replicate to make a chromosome
prophase
- chromosomes become visible
- centrioles move to opposite poles of the cell
- nuclear membrane disintegrates
Metaphase
- spindles fibres attach to chromosomes
- chromosomes line up along the equator
‘M’ is for middle
Anaphase
- chromatids are pulled apart by the spindle fibres, forming 2 sets of chromosomes
- ‘A’ is for apart
Telophase
- nuclear membrane forms around the new set of chromosomes
Cytokinesis
- the division of the cytoplasm that follows mitosis
- new cells are formed
Mitosis inputs
1 diploid cell (2 sets of chromosomes)
Mitosis outputs
2 diploid daughter cells, genetically identical to parent cells
Meiosis inputs
1 specialised diploid cell in testes/ ovaries
Meiosis outputs
4 haploid cells, genetically different gametes
mitosis advantages
- If the conditions are suitable and stable (i.e. the environment) then this organism can produce many genetically identical offspring. Well suited to the environment.
- No need for a mate
mitosis disadvantages
if environmental conditions change, then the whole species is at risk of extinction. (as they are genetically identical)
meiosis advantage
genetically different offspring (due to gametes produced by meiosis from 2 genetically different parents) therefore a species may be more likely to survive changing environments.
meiosis disadvantage
You have to have a mate.
crossing over
in prophase 1, homologous pairs can exchange genetic material resulting in genetically different gametes.
Independent assortment of chromosomes
the separation of one homologous pair has no influence on the separation of another homologous pair resulting in the mixing of maternal and paternal chromosomes in gametes.
Aneuploidy
resulting in one chromosome too few or one chromosome too many. It is caused by the non-disjunction of homologous chromosomes
non-disjunction
is when a pair of chromosomes fails to disjoin or segregate so that 2 copies of a chromosome are present in the gamete instead of usually one copy
Cell cycle
- G1, S, G2 -> interphase
- mitosis = nuclear division
- cytokinesis = cytoplasmic division
Gap 1
- cell growth, the cell is functioning, producing proteins. -> some of these proteins will be enzymes necessary for DNA replication
Synthesis
DNA replication occurs here in readiness for mitosis
Gap 2
Continued cell growth and producing proteins, necessary for mitosis
how many autosomes are there in a human ovum
22
how many chromosomes in a human sperm
23
Are sex chromosomes present in somatic cells
Yes
