DNA & Genetics Flashcards
What is the structure of DNA?
1) DNA organized around Histones (proteins) which together AKA Chromatin.
2) During Interphase, chromatin is arranged loosely to allow access to DNA but in Mitosis it’s packed tightly into units of Chromosomes.
3) When DNA replicates, the chromosome is composed of two Chromatids which are joined together at the Centromere.
Diploid vs. Haploid
1) Diploid is a somatic cell that has 2 sets of chromosomes (one from each parent).
2) Haploid is a cell with one set of chromosomes (sex cells/Gametes) because they haven’t paired with another cell yet.
DNA Replication & it’s 3 Steps (IET)
1) Initiation- an initiator protein binds to the DNA at origin sites & the DNA polymerase complex will attach. The enzyme helicase unwinds the DNA Into two seperate single strands.
2) Elongation- new strands of DNA are created. The leading strand can be easily copied but the lagging strand requires Okazaki Fragments to be synthesized.
3) Termination- when the replication forks meet the process is terminated
Telomere- the piece of DNA at the end of the strand that can never be read or replicated by DNA polymerase because it’s at the end.
4 Important Enzymes in DNA Replication
1) DNA Helicase- unwinds a section of DNA to create a segment with 2 single strangs.
2) DNA Polymerase- Polymerase 1 = synthesizes Okasaki fragments, Polymerase 3- responsible for primary replication of the 5’ to 3’ strand
3) DNA Ligase- fixes small breaks in the DNA strand & used to seal the finished DNA strands
4) DNA Telomerase- in some cells, allows DNA to be copied additional times by lengthening the Telomeres at the end of each DNA strand.
Transcription & Translation
Transcription- process of making mRNA from a DNA strand.Translation- converts the mRNA transcript into a useable protein (occurs in the ribosome) by binding to the appropriate tRNA.
Genotype vs. Phenotype
Genotype- genetic code
Phenotype- observable characteristics
People can have the different genotypes that present themselves as the same phenotype (Rr & RR)
Homozygous vs. Heterozygous
Homozygous- identical alleles (RR or rr)
Heterozygous- different alleles (Rr)
MENDEL’S LAWS (3)
1) Law of Segregation- genes come in allele pairs and that each parent can pass only a single allele down to its child.
2) Law of Independent Assortment- genes responsible for different traits are passed on independently. (mom may pass on gene of brown hair but not gene for height)
3) Law of Dominance- some alleles are dominant and some are recessive.
Genetic Cross
Method in genetic experimentation in which a scientist intentionally breeds two individual parent organisms in order to produce an offspring that carries genetic material from both parents.
Punnett Square
Diagram used to determine possibility an offspring will inherit a particular genotype (and resulting phenotype).
Monohybrid vs. Dihybrid Crosses
Monohybrid Crosses- P generation is selected based on one particular trait.
Dihybrid Crosses- P generation is selected based on two traits that differ between two parents. (EX: Mendel’s peas ..smooth & yellow and another of green & wrinkled).
4 Non-Mendelian Genetics (GSCI)
1) Gene Linkage- genes that are situated close together on a chromosome are likely to be inherited together. (all genes have a 50% chance of being inherited with another gene)
2) Sex-Linked Genes- genes that are only expressed when carrying either X or Y chromosome. EX: color blindness & Hemophilia are both X-linked disorders & are carried by females but appear more commonly in males)
3) Codominance- when 2 dominant alleles are inherited. EX: When a person has AB blood type (genes for both blood type A & B are dominant).
4) Incomplete Dominance- when one allele is not completely dominant over the other (blend).. EX: if flower color red is incompletely dominant over flower color white, offspring with both alleles will have pink flowers.
