inheritance 2022 Flashcards
genome
Entire DNA of an organism
Gene
Section or Molecule of DNA that codes for a specific protein
DNA molecule structure
Double helix formed of 2 strands linked by a series of paired bases: Adenine (A) with Thymine (T) and Cytosine (C) with Guanine(G)
RNA molecule structure
Single strand, contains Uracil (U) instead of Thymine (T)
First stage of of protein synthesis
Transcription
Transcription
1. The 2 DNA strands are separated and the nucleotide bases of the template strand are exposed
2. Free RNA nucleotides form complementary pairs with exposed DNA bases
a. Remember DNA has Uracil (U) not Thymine (T)
3. The adjacent RNA nucleotides are joined via bonds to form an mRNA molecule
4. When a gene has been transcribed, the mRNA molecule leaves the DNA and passes out of a nuclear pore to a ribosome in the cytoplasm
5. The 2 DNA strands re-join
Translation
- The mRNA molecule enters the ribosome
- At the ribosome, each mRNA codon is matched with a complementary anticodon on a tRNA molecule
- The ribosome catalyses the formation of a (peptide) bond between the amino acids, gradually forming a (polypeptide/amino acid) chain
- The amino acid/polypeptide chain is folded to form a functional protein
- The process continues until a stop codon is reached on the mRNA
chromosome
carries genetic information as DNA
Allele
a different form/version of the same gene
Dominant allele
represented by an upper-case letter (e.g. D); only 1 dominant allele is needed in the genotype for it to be expressed in the phenotype.
Recessive Allele
represented by a lower-case letter (e.g. d); 2 copies of the recessive allele are needed in the genotype to for it to be expressed in the phenotype.
Genotype
the genetic makeup of an individual regarding a particular feature; the alleles each cell has for a particular gene.
E.g. DD, Dd or dd.
Phenotype
the physical manifestation of a genotype.
E.g. dimples or no dimples.
Homozygous
an individual with 2 identical alleles for a particular gene, e.g. BB or dd.
Heterozygous
an individual with different alleles for a particular gene, e.g. Bb.
Codominance
When both allelles are expressed in the phenotype
Polygenic inheritance
Most phenotypes are expressed as the result of multiple alleles in multiple genes
- Mitosis happens in my toesies
Mitosis
stages
cell division in normal body cells, for growth and repair/replacement, or asexual reproduction in some organisms
o Mitosis produces 2 genetically identical daughter cells
Interphase The cell spends most of its life in this phase. The DNA in chromosomes copies itself ready for mitosis.
Prophase The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears.
Metaphase Chromosomes and their copies line up in the middle of the cell.
Anaphase Chromosomes and their copies are pulled to different ends of the cell.
Telophase New membranes form around the chromosomes at each end of the cell.
Cytokinesis The cell membrane pinches in and eventually divides into two daughter cells.
Meiosis happens in my ovaries/testes
Meiosis
cell division to produce sex cells (gametes) for sexual reproduction
Gamete
Sex cell with 1 set of chromosomes, 1 from each homologous pair
Haploid cells
Half the number of chromosomes
number of chromosomes in humans
23 pairs
karyotype
The number and visual appearance of the chromosomes in the cell nuclei of an organism
Homologous pair of chromosomes
- One from the father (the paternal chromosome)
- One from the mother (the maternal chromosome)
- Each carries the same genes in the same order (so are a similar length), but the alleles for each trait may not be the same
- In the human karyotype, there is
o 22 pairs of autosomes
o 1 pair of sex chromosomes
Effects of genetic mutations
most genetic mutations have no effect on the phenotype, some have a small effect and rarely do they have a significant effect (frameshift)
Change in DNA can..
change the phenotype by altering the sequence of amino acids in a protein
Mutation chances increased by..
by exposure to ionising radiation (for example, gamma rays, x-rays and ultraviolet rays) and some chemical mutagens (for example, chemicals in tobacco)
Evolution
is the slow, continual change of organisms over a very long time – Charles Darwin
Mutation:
A change in DNA, which may result in an organism having different characteristics
