genetic processes Flashcards
DNA replication
Both mitosis and meiosis involve replication of DNA before the division begins. This ensures that each daughter cell receives a complete set of genetic
Cell Division
Both processes result in formation of new cells, contributing to growth, repair and maintenance of organisms.
Chromosomes
Chromosomes are present in both mitosis and meiosis.
Purpose
Mitosis, is primarily for growth, repair and maintenance of somatic cells. That resulted in two identical daughter cells. Meiosis is sexual reproduction cells. The end result is four non - identical daughter cells, each with half the chromosome number of the parent cell.
Occurrence
Mitosis: Occurs in somatic cells throughout an organism’s life
Meiosis: Occurs in germ cells (Sperm and egg cells) during the formation of gamates for sexual reproduction.
Prophase
chromosome replication, nuclear membrane dissolves
Metaphase
sister chromatids line up along middle of cell by spindle fibres
Anaphase
spindle fibres pull daughter chromosomes to opposite ends of cells
Telophase
cytokinesis creates 2 identical daughter cells
Crossing over
It occurs in meiosis Prophase I, in order to exchange genetic information between homologous pairs to induce variation in the genetics of daughter cells.
Genotype
A person’s genotype is their unique sequence of DNA. The two forms a person has inherited from their mother and father, for a particular gene. (ex. HH or Hh, or hh )
Phenotype
Observable expressions of this genotype. (Ex. Hh, they have the recessive trait for hair but with the dominant uppercase H, they have hair showing) (hh is recessive and have no hair)
Gene
A part of a chromosome that governs the expression of trait and is passed on to the offspring; it has a specific DNA sequence.
Allele
The alternate forms of a gene
Dominant
The form of a trait that will always appear (be expressed) when an individual has an allele for it. If one dominant allele is present, then dominant trait will be expressed Ex:
Rr or RR = round pea.
Recessive
The form of a trait that will only appear (be expressed) if the individual has 2 alleles for it. Ex: rr = wrinkled pea
Trait
Specific Characteristics of an individual
Diploid
refers to twice the number of chromosomes in a gamete (2N). Every cell of the body is diploid except sex cells. In humans the diploid number of chromosomes is 46
Haploid
refers to the number of chromosomes in a gamete . Referred to as N. In humans the haploid number of chromosomes it is 23
Homozygous
describes the genotype of an individual with two alleles that are the same, ex. RR or rr
RR = homozygous dominant
rr = homozygous recessive
Heterozygous
describes the genotype of an individual with two alleles that are different,
Ex. Rr the phenotypic expression (observed trait) is always the dominant allele.
Codominance
both allele are present (black and white makes black and white spots)
Incomplete
intermediate allele is expressed in heterozygous situation (black and white makes grey) (The colours “Mix”)
Homologous chromosomes
paired chromosomes similar in size, shape , gene arrangement and gene formation
A (AA,AO)
Can receive from: A,O
Can donate to: A,AB
B (BB,BO)
Can receive from: B,O
Can donate to: B,AB
AB (AB)
Can receive from: All (universal recipient)
Can donate to: AB
O (OO)
Can receive from: O
Can donate to: All (universal donor)
Non - disjunction
the failure of homologus chromosomes pairs or sister chromatids to separate during Anaphase I or II of meiosis.
Monosomy
The loss of a chromosome as a result of non-disjunction
- Most common in chromosome 21, 13, 18
Trisomy
The gain of an extra chromosome as a result of non-disjunction
Klinefelter - XXY
Boys are grown with an extra X chromosome. Sexual Immaturity, inability to produce sperm, breast swelling
Turner - XO (1 X chromosme only)
Short Stature, Webbed neck, Sexually underdeveloped
Downs (Trisomy 21 - Gains an extra chromosome)
Intellectual disabilities, abnormal patterns of palm creases, almond - shaped eyes, flattened face, short stature
