Chapter 2 - Processes for continuity of life Flashcards
what are the three parts of a nucleotide
a five carbon sugar, a phosphate group and a nitrogenous base
what is a nucleotide
building blocks of DNA and RNA linked together by phosphodiester bonds
what is DNA
A double stranded helix that determines the characteristics that define species
Asexual reproduction and what does it result in
Offspring produced without the fusion of gametes. Results in identical offspring closely resembling parents due to one source of inherited information
sexual reproduction
reproduction in which offspring are produced from two parents by the fusion of male and female gametes
Eukaryotic cell
complex cell containing many membrane bound organelles, DNA found in nucleus, mitochondria and chloroplasts
What are the levels of organisation of a human chromosome
DNA is wrapped around histones, creating nucleosomes. This loosely coiled form of DNA and protein is called chromatin. Chromatin condenses to form chromosomes in preparation for mitosis or meiosis
Centriole
rod shaped organelle that helps make the spindle fibres for cell division
Centromere
Waist like constriction in a chromosome where the spindle fibres attach. enables the movement of chromosomes during cell division
Centrosome
Contains two centrioles, duplicates during cell division and separates to opposite poles. Produces spindle fibres
Chromatid
Daughter strand of duplicated chromosome that is joined to another chromatid by a centromere
Chromatin
Loosely coiled form of DNA and protein (histones) found in non diving cells. Supercoils to become chromosomes
Chromosome
Structure composed of DNA and protein that carries genetic information
Gene
unit of heredity that transmits info from one generation to the next
Autosome
matched homologous pairs of non sex chromosomes
how many chromosomes do humans have
46 (23 pairs, 22 are matched)
Heterosome
unmatched homologous pairs of sex chromosomes (XY)
Germline cells
A specialised sex cell that gives rise to gametes. early in development, specialise into male or female germ cells
Differentiation
Process where newly formed cells become more specialised as they mature
Diploid (2n)
Cell or organism that has a genome containing two copies of each chromosome
Haploid (n)
Cell or organism that has a genome containing one copy of each chromosome
Locus
the position a gene occupies on a chromosome
Allele
One of the various versions of the same gene
Prokaryotes
Single celled organism lacking membrane bound organelles such as a nucleus. DNA found in cytosol (in nucleoid)
Plasmid
Small circular piece of DNA found in bacteria that is able to replicate independently of the cell’s chromosomes
Mitosis
Type of nuclear division occurring in somatic cells that maintains the parental diploid number of chromosomes in daughter cells. Results in the formation of two diploid daughter cells with identical sets of chromosomes. Little variation
Why are the terms parent and daughter cells used
For communication purposes to help distinguish the original cell from newly formed cells
Meiosis
Eukaryotic cell division concerned with the production of gametes (sex cells) in sexually reproducing organisms. Involves one cycle DNA replication and two rounds of cell division, resulting in four haploid daughter cells from each original diploid parent
Cell cycle (6 phases)
- The sequence of events from one cell division to another.
- Interphase (G1, S, G2), M phase, C phase (nuclear division and cytokinesis) and G0 phase
What happens at each cell cycle stage?
(G1, S, G2, M, C, G0)
- M phase: cell and nuclear division
- C phase: cytokinesis
- G0 phase: Non-proliferating state, undergoing extended G1, but are not preparing to replicate DNA and divide
- G1 phase: Period of metabolic activity and growth
- S phase: Duplication of chromosomes and centrosomes (DNA replication)
- G2 phase: Further growth and reproduction of organelles as cell prepares to divide
Interphase
Stage between cell divisions. includes G1, S phase and G2
Four main phases of mitosis
Prophase, Metaphase, Anaphase, Telophase
PMAT. SEE OTHER DECK FOR DEFINITION OF EACH
Cytokinesis in plant cells
Cytoplasm divides with formation of cell plate (structure in place where new cell wall is forming)
Cytokinesis in animal cells
Cytoplasm divides by a process known as cleavage. Cell membrane around middle of cell draws together to form a cleavage furrow
how is the cell plate formed
Parts of the cell wall fuse with parts of the spindle
Binary fission
Process of asexual reproduction whereby prokaryotic cell divides into two identical daughter cells. Includes DNA replication, chromosome segregation and cytokinesis. Produces daughter cells with same number of chromosomes as parental cell
What are the six steps of binary fission
- Prior to binary fusion, the single chromosome is tightly coiled
- Genetic material, chromosome and any plasmid replicates and separates
- Original and replicate chromosomes attach to cell membrane and pulled to separate polls as cell elongates
- New cell wall starts to grow, cleavage furrow develops
- New cell wall fully develops
- Two cells separate (cytokinesis), forming two identical daughter cells. Chromosomes become tightly coiled again
what causes variation in offspring
crossing over and random assortment of chromosomes during meiosis
Bivalent
a structure made up of two homologous chromosomes joined together
Synapsis
The pairing of homologous chromosomes during prophase 1
Crossing over
The exchange of genetic material between maternal and paternal chromosomes that occurs during prophase 1
What causes independent assortment
Random orientation of maternal and paternal homologous chromosomes during metaphase one
Fertilisation
The joining together of two gametes to form a zygote.. Zygote receives one of each of its pairs of chromosomes from each parent
Apoptosis
Program series of events that leads to a cell death.
What are the differences between mitosis and meiosis
- Function: In mitosis, nuclear and cellular division for growth, repair and replacement of tissues. In meiosis, Nuclear and cellular division for producing gametes
- Number of cell divisions: In mitosis, one. In meiosis, Two
- Number of chr in daughter cells: In mitosis, Each two identical daughter cells contains diploid number of chromosomes. In meiosis, Each four, non identical daughter cells contains haploid number of chromosomes
- Variation: In mitosis, no variation unless due to environmental influences or mutations. In meiosis, Variation due to crossing over (Prophase one) an independent assortment (Metaphase one)
- Diversity: In mitosis, Diversity of offspring does not increase. In meiosis, diversity of offspring is increased
- Cells involved: In mitosis, Somatic cells (body cells). In meiosis, germline cells
What are the inputs and outputs of meiosis
- Inputs: Adult female (2n) and adult male (2n)
- Meiosis
- Outputs: Egg (n) and sperm (n)
- Zygote (2n)
- Mitosis
- Growth and development
