Chapter 7 - Heredity Flashcards
What is chromatin?
Substance that makes up chromosones (DNA + Protein (Histones))
What are Histones?
Small proteins which DNA wraps around to create chromatin.
What are germline cells?
Somatic cells whose specify role is to undergo meiosis and create gametes.
Autosomal chromosones
Non- sex determining chromosome
What are somatic cells?
Diploid (2N), non sex cells with a set of paired chromosones
Base pairings?
Guanine & Cytosine
Adenine & Thymine
What direction in terms of 5’ and 3’ does DNA travel and where are the 5’ and 3’ located in terms of chemical structure.
DNA travels 5’—> 3’
5’ : pentose sugar & Phosphate (same monomer)
3’ : pentose sugar & Phosphate (different monomer)
Bond between DNA monomers?
Phosphodiesther bond
Differences between DNA and RNA
DNA : double stranded, one less oxygen in ribose, carries all genetic info
RNA: single stranded, thymine replaced by uracil, carries only info required for protein synthesis
4 steps from DNA —> Protein
Unwinding
Transcription (pairing)
Splicing
Translation
Steps of cell cycle in order:
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Interphase
How does binary fusion occur?
Single DNA chromosome is replicated, following which the identical chromosomes are separated allowing a cell wall to form before cell splits into two identical cells.
Prophase:
Nuclear membrane disintegrates
chromatin condenses revealing chromosomes
centrioles move to poles and spindles form
Metaphase:
Chromosomes attach to spindle fibres and align themselves at equator.
Anaphase:
Chromatids are pulled apart towards the poles.
telophase: (Animal & Plant)
Nuclear membrane forms creating two nuclei.
chromosomes begin to lengthen and disappear
Animal: Cell membranes cleave
Plant: Cell plates form
cytokinesis: (animal & plant)
Animal: cells are cleaved. Two cells remain
Plant: Cell plates extend to meet cell wall. Two cells remain
Meiosis 1:
Chromosomes appear
Nuclear membrane disintegrates
Crossing over can occur
Centrioles move to poles
Metaphase 1;
Homologous chromosomes (bivalents) line up independently along equator in pairs. Crossing over occurs
Anaphase 1:
Homologous chromosomes seperate apart (Disjunction)
Telophase 1:
Cell division
Now remain 2, 1n cells
DNA replication process.
Helicase : splits & unwinds DNA
DNA polymerase 3, synthesises DNA on Leading strand.
On complementary strand:
RNA Polymerase, makes short RNA primer
DNA polymerase 3 synthesises Okazaki fragments
DNA polymerase 2 digests RNA primer and replace with DNA
DNA lipase join Okazaki fragments into continuous strand
Meiosis division 1 summary:
Chromosomes appear in prophase and align in homologous pairs at equator in metaphase. Crossing over occurs before homologous chromosomes separate in anaphase and cleave into two cells in telophase. Both remaining cells are haploid.
Meiosis division 2 summary:
Spindles form at right angles to before meaning chromosomes align independently along equator 90° to before during metaphase 2. Chromatids separate in anaphase 2 and cleave into 4 seperate haploid gametes during telophase 2 and cytokinesis.
Why is DNA replication semi-conservative.
Both strands of original DNA helix act as template for DNA replication.
The two new DNA Helixes both have one strand from the original helix and new one and are hence semi-conservative.
Triplet vs Codon Vs anticodon
Three DNA bases coding for one amino acid = Triplet.
Three mRNA bases coding for one amino acid = codon
Three tRNA bases coding for one amino acid = anti-codon
How genetic diversity occurs
- Chromosomes align independently in metaphase 1 (& 2?)
- Crossing over metaphase 1 (sometimes P1)
Mendel’s Law of Independant Assortment
During Meiosis chromosomes and subsequent alleles align and separate randomly resulting in a random assortment of alleles in gamete production.
Mendel’s law of segregation;
Each pair of alleles will separate independently during gamete formation. When sperm and egg fertilise each contributes an allele to the offspring which is 2n.
Allele Vs Gene
- Gene a sequence of DNA which codes for the production of a protein
- Allele is a varient form of a gene located at a gene loci and codes for a particular phenotype.
codominance
Both alleles are fully expressed in phenotype
Black + White = Black & white striped
Why do various heights occur?
- Height is polygenetic and is influenced by multiple genes.
- Height is also influenced by a range of environmental factors.
- This results in continuous variation rather than discontinuous variation.
Clues for sex linked recessive
- In general males effected more
- Female usually carriers, males cannot carry
Clues for autosomal recessive Vs autosomal dominant
Recessive: Possible for allele to be carried
Dominant: allele cannot be carried
Clues for sex linked dominant
effect males pass on trait to all females
AB ab ---- & ----- ab ab Gametes of each paretn Parental & recombinant genes
Gamete P1: AB & ab
Gamete P2: ab
Parental: ab/ab or AB/ab
Recombinant: Ab/ab or Ba/ab
S Phase of mitosis
DNA replication (synthesis)
G2 Phase of mitosis
Cell prepares for cell division
Chromosomes begin to condense
G1 Phase of mitosis
Cell growth
before DNA replication
Phases of Cell cycle
G1 —> S –> G2 —> Mitosis –> Mitosis
