Genetics: Cells Flashcards
What are the three stages of the cell cycle in order?
Interphase, mitosis, cytokinesis
What stage of the cell cycle is the longest?
Interphase
What are the four phases of mitosis
Prophase, metaphase, anaphase, telophase
What 3 parts make up a nucleotide?
Deoxyribose sugar (pentagonal), phosphate group (circular), one of four nitrogenous bases (rectangular)
When nucleotides are linked together, what molecule is created?
Nucleic acids (DNA or RNA)
What shape is created when nucleotides link together?
Double-helix
Name the four nitrogenous bases used to create a DNA molecule
Purines: adenine, guanine
Pyramidines: thymine, cytosine
What is complimentary base pairing?
When two complimentary strands of DNA link up, adenine can only pair with thymine and guanine can only pair with cytosine because of their size and attraction
Describe the relationship between DNA, chromatin, chromosomes, genes, alleles, homologous chromosomes, and sister chromatids
DNA is the molecule that carries genetic instructions. Chromatin is the thin complex of DNA and proteins. Chromosomes are condensed structures made of chromatin. Genes are segments of DNA that code for a trait. Alleles are different versions of a gene. Homologous chromosomes are chromosome pairs. Sister chromatids are replicated copies of a chromosome
What are the two purposes of meiosis?
Genetic reduction: meiosis begins in diploid cells with the aim of producing haploid cells
Genetic recombination: creates sex cells that have a different combination of alleles by recombining the alleles in homologous chromosomes
What is crossing over?
Occurs in prophase I. Homologous chromosomes line up side-by-side in an alignment called synapsis, which forms a tetrad. They can then swap sections of genetic code between these chromosomes (genetic recombination). It can occur anywhere and in any amount among homologous pairs
What are the phases of meiosis?
Meiosis I: prophase I, metaphase I, anaphase I, telophase I
Meiosis II: prophase II, metaphase II, anaphase II, telophase II
Explain the difference between oogenesis and spermatogenesis
Oogenesis: meiosis in females. Begins before birth up to prophase I, then starting at puberty, one cell will complete meiosis each month until menopause. Takes a diploid oogonia and creates two polar bodies and one healthy egg cell. This is due to uneven distribution of cytoplasm
Spermatogenesis: meiosis in males. Takes a diploid spermatogonia cell and produces four haploid sperm. Begins at puberty and continues throughout life
What are some errors that can occur during crossing over?
Cri du Chat: deletion of a section of chromosome
Charcot-Marie-Tooth disease: duplication of a section of a chromosome (chromosomes 17 is longer, leading to low muscle definition, numbness, discoordination)
FG syndrome: inversion of a section of a chromosome (occurs only in males, leading to low muscle tones)
Chronic Myelogonous Leukemia: translocation of a section to a different chromosome (piece of chromosome 9 gets added to chromosome 22)
What is nondisjunction?
An error in the number of chromosomes, in which homologous chromosomes do not separate during anaphase I or when sister chromatids do not separate properly during anaphase II. The result is the production of sex cells that have either too few or too many chromosomes. Nondisjunction disorders increase with age, significantly in 40+ aged women
What is the name of the disorder that is Trisomy 21?
Down Syndrome
Describe prophase
No nucleus, chromatin condenses into visible chromosomes, centrioles move towards the poles and begin forming spindle fibres, nuclear membrane begins to disappear
Describe metaphase
Nuclear membrane completely dissolved, chromosomes line along the equator of the cell, spindle fibres attach to the centromeres of each chromosomes
Describe anaphase
Sister chromatids are pulled apart at the centromere towards opposite ends of the cell by the spindle fibres
Describe telophase
The chromosomes have reached the opposite ends of the cells, they start to unwind becoming less visible, nuclear membrane and nucleolus forms around each set
Describe interphase
Cells carry out their normal functions, grows, makes copies of its genetic material
What are the three stages of interphase?
G1, S-phase, G2
Describe the G1 stage of interphase
Major period of growth
Describe the S-phase of interphase
DNA (in its long, stringy form called chromatin at this time) is replicated
Describe the G2 stage of interphase
Further growth and molecule synthesis in preparation for mitosis, the cell is still carrying out its normal functions during all these phases