Chapter 9-12 Flashcards
Monoploid
Haploid, a cell that contains only 1 set of chromosomes. (n) occurs in gametes
Diploid
A cell that contains 2 sets of chromosomes. (2N) occurs in fertilization or mitosis
Gametes
Sex cells, sperm and eggs. Which are monoploid, produced by meiosis
Somatic Cells
Regular body cells, are diploid. Produced by mitosis
Mitosis
Type of cell division
Interphase
Phase when cells are not dividing
G1 phase
Stage of rapid growth, centrioles replicate, organelles replicate
S phase
Stage in which dna duplicates
G2 phase
Growth and final cell preparation for cell division stage
Chromosomes
Packages of DNA, somatic cells have 46, sex cells have 23. Contain DNA and proteins called histones.
Chromatin
Uncondensed DNA, condenses during cell division to for chromosomes
Mitotic cell division
Refers to the division of the nucleus, occurs in 4 stages (prophase, metaphase, anaphase, and telophase), daughter cells are identical
Cytokinesis
Division of the cytoplasm, occurs after the nucleus has divided (telophase)
Early Prophase (Mitosis)
Nucleoli dissolve, chromatin condenses to form discrete chromosomes, spindle fibres form between the centrioles, centrioles begin to move to opposite poles of the cell
Late prophase (Mitosis)
Nuclear membrane dissolves, centrioles move to opposite poles of the cell, spindle fibres extend between poles of the cell, sister chromatids condense, sister chromatids are held together by a centromere
Metaphase (Mitosis)
Sister chromatids line up at the metaphase plate, centromeres align along metaphase plate, chromatids line up with long axis at right angles to the spindle
Anaphase (Mitosis)
Paired centromeres begin to move apart, sister chromatids begin to separate at their centromere, chromatids line up with long axis at right angles to the spindle
Telophase (Mitosis)
Nuclear membrane reforms, nucleoli reform, cytokinesis divides the cytoplasm into equal parts. (Cleavage furrow in animals, cell plate in plants)
Cancer
A mutation when DNA begins to divide continuously, rapidly dividing cell.
Meiosis
Reduction division, formation of gametes (sperm and eggs). One DNA replication and 2 nuclear divisions. The resulting cells are haploid, they have half the number of chromosomes as a regular somatic cell
Importance of meiosis
Produces haploid gametes and therefore keeps the chromosome number constant when fertilization takes place. A source of genetic variation
Homologous Chromosomes
Each pair of chromosomes (partner), chromosomes that contain genes for the same trait one from the father and one from the mother
Sex chromosomes
Females XX chromosomes, male XY chromosomes
Somatic cells
Diploid cells containing 46 chromosomes (44 autosomal chromosomes and 2 sex chromosomes). 2 sets of chromosomes, one maternal and one paternal. 23 pairs of homologous chromosomes produced by mitosis
Gametic cells
Monoploid or haploid cells containing 22 autosomes and 1 sex chromosome. One set of chromosomes with genetic variability, produced by meiosis
Interphase (Meiosis)
Each chromosome produces an exact replica of itself, each pair now consists of sister chromatids that are genetically identical, sister chromatids are attached at their centromere, centrioles replicate
Prophase 1 (meiosis)
Chromosome threads condense, homologous chromosomes synapse forming a tetrad. Homologous chromosomes may undergo crossing over between sister chromatids, centriole pairs move to opposite poles and nuclear membrane disperses
Tetrads
Synapsed pairs of homologous chromosomes
Chiasmata
Points of contact between homologous chromosomes where genetic material can be exchanged
Metaphase 1 (meiosis)
Chromosome Tetrads align themselves on the metaphase plate, the centromeres of the homologous chromosomes point towards opposite poles of the cell
Anaphase 1 (meiosis)
Homologous pairs separate and move to opposite poles of the cell, sister chromatids remain attached at their centromeres, spindle fibres guide homologous pairs to opposite poles
Telophase 1 (meiosis)
Homologous chromosome pairs separate and reach poles of cells, each pair still consists of two sister chromatids, cytokinesis divides cytoplasm, nuclear membrane may form and each pole receives a haploid set of homologous chromosomes
Prophase 2 (meiosis)
If there is a period of time between meiosis 1 and 2 the nuclear membrane and nucleoli disappear. Centrioles and new spindle apparatus appear and move to opposite poles of the cell
Metaphase 2 (meiosis)
Sister chromatids align themselves along the metaphase plate
Anaphase 2 (meiosis)
Centromeres of sister chromatids divide, sister chromatids separate and move to opposite poles of the cell, movement of sister chromatids is guided by spindle fibres
Telophase 2 (meiosis)
Division of the cytoplasm (cytokinesis), new nuclear membrane are reassembled around each set of chromosomes, four haploid cells are formed. All gametes are genetically distinct.
Nondisjunction
Mix up in meiosis, gametes will be created with to many or too few chromosomes
Nondisjunction in meiosis 1
2 gametes will have an extra chromosome and 2 gametes will be missing a chromosome
Nondisjunction in meiosis 2
2 gametes will be normal, one will have an extra chromosome and one will have a missing chromosome
Chromosomes numbers
Chromosomes have been numbered 1-23 for identification, partner chromosome have the same structure and carry the same genes therefore are no counted twice
How is gender determined
During oogenesis ova receive one X chromosome, during spermatogenesis sperm receive one X or one Y chromosome. Upon fertilization the presence of a Y chromosome leads to make development
X chromosome
Carries more than 2300 genes, most deal with nonsexual traits. Genes on X chromosome can be expressed in both males and females
Y chromosome
Fewer than 2 dozen genes, one is the master gene for male sex determination (SRY gene) SRY present= testes form, SRY absent= ovaries form
Turner Syndrome
Inheritance of only one X chromosome (XO), survivors are short infertile females and secondary sex traits are reduced
Klinefelter Syndrome
XXY condition, results mainly from nondisjunction in mothers. Tall sterile males, feminized traits
Jacobs syndrome
XYY, Nondisjunction in the father. Taller than average males, phenotypic ally normal because Y chromosome is much smaller
Down syndrome
Trisomy of chromosome 21, mental impairment and a variety of additional defects. Risk of Down syndrome increases in mothers over age 35
Edwards syndrome
Trisomy of chromosome 18
Patau syndrome
Trisomy 13, most will not survive long
Karyotyping
A way of examining the chromosomes of an unborn child to determine if there is a chromosomal abnormality
Amniocentesis
Procedure by which a needle is used to withdraw a small sample of amniotic fluid from the uterus to perform genetic analysis. For safety cannot be performed until the 14th week of pregnancy
Chorionic villus sampling
Can be performed around 9 weeks, involves inserting a suction tube into the mothers uterus and taking a small sample of placenta, (placenta originated from the embryo itself so has I the same DNA as the fetus), chromosomes are then analyzed
Karyotype preparation
Collected cells are arrested at metaphase by adding colchicine, cells are most condensed and easiest to identify. Chromosomes are stained and photographed through a microscope and then cut up and arranged into a karyotype
Asexual reproduction
Mitosis is key, allows for large number of offspring in a short period of time, offspring are identical to the parent, requires less energy, no genetic variability
Budding
A complete but miniature version of adult grows out from parents body
Vegetative reproduction
A plants stem grows out and a new plant develops at end of stem
Fragmentation
New individual grows from a fragment of another individual
Parthenogenesis
An unfertilized egg develops into an adult
Spores
Seed like structures that can be dispersed and will grow into individuals
Alternation of generations
Life cycle of plants consists of two generations, diploid one and haploid one. Sporophyte produces haploid spores through meiosis, grows into haploid individual, (gametophyte) produces gametes that undergo fertilization to produce new sporophyte
Diploid>haploid>diploid>haploid
Sporophyte
Diploid generation in plants
Gametophyte
a haploid individual in plants (spore grows without being fertilized)