Lecture 6: Chromosomes, Recombination, DNA Flashcards
chromosomes
-found within a cell nucleus made of DNA that contains genes
how many chromosomes do humans have?
-46 chromosomes total, 23 from mom and dad
karyotype
-a map of a set of chromosomes
chromatid
-each half of a duplicated chromosome
sister chromatids
-just before cell division the DNA material replicaes and 2 chromatids, each with identical information on them, are paired
centromere
- holds sister chromatids together
- central part of the chromosome
homologous pair
-when one chromosome from both parents form a doubled pair
ploidy
-number of copies of chromosomes
sex chromosomes
- one of the two chromosomes that determine an individual’s sex
- females have 2 X chromosomes; malse have one X and one Y chromosome
crossing over
-the mutual exchange of segments of genetic material btwn non-sister chromatids of two homologous chromosomes so as to produce
recombination
-process by which the combinations of alleles for different genes in two parental individuals become stuffed into new combinations in offsprings individuals
how do chromosomes explain gene linkage?
- whether or not traits are linked determes what gamete combinations can be produced
- but this is also determined by how close genes are on a chromosome
does recombination eliminate gene linkage?
-no because depending on the location of the genes on the chromosome determines which genes are more likely to be together
the basic structure of DNA
-two intertwined helical strands of nucleotides held together by hydrogen bonds (aka double helix)
nucleotides types
- adenine(A)=thymine(T)
- cytosine(C)=guanine(G)
loosely linked genes
- futher apart distance of genes on a chromosome
- higher likelyhood that recombinatin will end up separating them
how does DNA replicate?
-a single strand of parental DNA w two chains can give rise to two daughter strains that will contain the exact info as the parental strand, due to complimentary pairing
what is the central dogma of molecular biology?
-portions of DNA (the genes) get converted into RNA which provide instructions to the cell for the production of protein
what do comparisons of amino acid sequences (cytochrome C), gene functions, or DNA sequences tell us about organism relatedness?
- when you sequence the amino acids for a particular protein from a variety of organisms, you can look to see how the amino acids have changed to see how closely related they are
- -> the most popular amino acid sequence to use to see that^ is cytochrome C
- -> its in all living things and is small which make it useful in studies of evolutionary relatedness
transcription
- process of copying DNA into RNA
- occurs inside nucleus
translation
- process of turning RNA into protein
- occurs outside nucleus
how are proteins formed?
- DNA–>RNA–>protein
- copies of the “instructions” (DNA) are made and the single stranded copies of the DNA are now RNA
- RNA leaves the nucleus to instruct other organelles to make the proteins, which then can go wherever they’re needed to do the work of the cell
basics of mitosis
- DNA condenses and replicates, cytoskeleton disassembles, mitosis spindle forms, chromosomes align along spindle (1 copy each), sister chromosomes separate on ends of all and cell break in half
- ->cells will be identical
basics of meiosis
-DNA replicate and condense, meiotis spindle forms, homologous pairs form and join, crossing over occurs, 1 chromosome pulls apart and sister chromosomes stay together, chromosomes align again and divide, 4 cells result
cell outcomes/differences
- mitosis: 2 cells result, all diploid, cells will be identical, chromosomes line up in single file
- meiosis: 4 gametes results, all haploid, cells won’t be identical, chromosomes line up in middle in homologous pairs
