Unit 3: Genetics Flashcards
Hybrid
An individual produced by two genetically different individuals. Heterozygous.
Punnet Square
A diagram used to predict the phenotypes in a particual breeding/cross experiment
Trait
A characteristic in an individual or species. Determined in genetics by genes.
Allele
One or more versions on a set of DNA in a specific location.
Locus
The physical site of a specific gene on a chromosome. E.g DNA from a specific locus was deleted to produce a mutation.
Purebred
An individual with two identical alleles for a trait. Homozygous.
True breeding
An organism which always passes down specific phenotypes to its offspring.
Incomplete dominance
When one allele does not fully dominate producing a phenotype where both alleles can be seen at the same time. (in between parent phenotypes). Red and white flowers producing pink.
Codominance
When two seperate alles are expressed seperately in an individual. Usually producing spots. Red and white flowers producing a red and white spotted flower.
P generation
F1 generation
F2 generation
- The parent generation (individuals being crossed)
- First filial generation (children of parents)
- Second filial generation (grandchildren of parents)
Gregor Mendel
Medel 1822 - 1884
Discovered the law of inheritance. He discovered that genes come in pairs and are inherited individually one from each parent.
Law of Dominance
If heterozygous only the dominant allele is expressed.
Law of Segregation
During gamete formation genes seperate so that each gamate carries only on allele for each gene.
Law of Independant Assortment
The allele a gamete receives for one gene doesn’t influence the alles for another gene.
Multiple alleles
Alleles are the alternate forms of the same gene so they influence the same trait.
Nucleotides
A molecule composed of a nitrogen base, a pentose sugar, and a phosphate. Any of the basic units of DNA or RNA. (a group of nitrogen base pairs)
Codon
3 nucleotides which form a unit of genetic code.
Nitrogen base
A nitrogen compound which forms an important part of nucleotides. ( Nucleobases: adenine cytosine guanine thymine)
Cell Cycle
A series of events which takes place as a cell grows and divides.
Interphase
G1 - Cell is growing and going through normal cell processes (longest)
S - DNA is replicated
G2 - Organelles and proteins necessary for cell division are produced (shortest)
Cytokinesis
At the end of meiosis or mitosis when the ceel finally splits into two daghter cell.
In animal cells - cells pinch
In plants - cell plate will form
Haploid
All gamates. Only sex cells. Have 26 chromosomes. Have half the number of chromosomes as the parent cell N.
Diploid
All other cells. Have 46 chromosomes. 2N
Homologous Chromosomes
Have the same genes in identical locations (locus’s). 2 chromosomes in a pair. (one from mother one from father. (think pairs in karyotyping) All together they are considered a full set of chromosomes 46.
Polyploidy
When a diploid cell or organism obtains an additional set of chromosomes.
Karyotype
The general apperance of the complete set of chromosomes in a cell or organism. (also refers to a labroratoy produces image of a persons chromosomes arranged in size order).
Monohybrid cross
A mating experiment between two organisms with different variation of one locus. (2 alleles for 1 trait)
Dihybrid cross
A mating experiment between two organisms which are identically hybrid for two traits. How two different genes are passed on from a pair of organisms.
Genes
The basic unit of heredity. Genes are made up of sequences of DNA and are at specific locations (locus) on chromosomes.
DNA structure
Two strands linked together called a double helix. Made up of pentose sugar, a phosphate, and a nucleobase/ nitrogen base (adenine cytosine guanine thymine)
Mitosis
Cell division that results in two identical daughter cells with 46 chromosomes each. Asexual
Meiosis
Cell division that results in 4 different haploid daughter cells with 23 chromosomes each. Produces the gametes. Sexual.
Chromosome
Made of two sister chromatids held together by a centromere. Thread like made of nucleic acid holding DNA and genetic information in the form of genes.
Prophase (mitosis, 1, and 2)
P - chromatin condenses to form chromosomes, nuclear membrane dissolves, nucleolus dissapears, centrioles move to poles, spindle fibers start to form,
P1 - same - chromosomes line up side by side in synapsis and form tetrads, crossing over occurs
P2 - same - but with haploid cells and no crossing over
Metaphase (all)
M - chromosome sline up in center of cell, spindle fibers attach to centromere
M1 - same
M2 - same
Anaphase (all)
A - chromosomes are pulled to the side of the cell by the spindle fibers they are seperated into chromatids (not in A1)
A1 - chromosome pairs split but not the centromeres
A2 - centrioles split and individual chromosomes are split into chromatids and pulled to sides of cell
Telophase (all)
T - chromosomes begin to uncoil, spindle fibers dissapear, new nuclear envelope forms around each region, new nuclei forms
T1 - same
T2 - same but with 4 haploid cells
Crossing over
The exchange of DNA between pairs homologous chromosomes. Produces genetic diversity.
Non-disjunction
The failure of chromosomes of chromatids to seperate succesfully. Resulting in abnormal chromosome distribution.
Tetrad
The link between homologous chromosomes consisting of 4 chromatids.
Monosomy
The absense of one member of a pair of chromosomes. 45 chromosomes in each cell. Usually due to non disjunction.
Trisomy
The addition of one extra chromosome in one or all of the body cells. (e.g down syndrom is extra chromosome 21)
Sex chromosome
The type of chromosome determining sex. XX - female, XY - Male.
Sex-linked characteristic
Genes carried on the sex chromsomes. Males are more affected by genes on the X chromosome because they only have one.
X-linked recessive inheritance
Will always be expressed in males if carrier but only expressed in females when they are homozygous for the trait.
Autosomal inheritance
The inheritance of traits determined by genes on the autosomal chromosomes (1-22)
Autosomal dominant
The inheritance of a dominant phenotype whose gene is on a autosomal chromosome. Two parents affected can produce a non affected child.
Autosomal recessive
The inheritance of a recessive phenotype whose gene is on a autosomal chromosome. Two parents not affected can produce an affected child.
Centriole vs. centromere
Produces spindle fibers in mitosis and meiosis. Centromeres hold the chromatids together.
Oogenesis/oocyte/ovum
The production of egg cells though meiosis in the egg cells. An oocyte is a cell that can produce more egg cells. The ovum is a single cell which when fertilized by the spermatozoa can develope a new organism.
Spermatogenesis/spermatocyte/spermatozoa
The production of sperm cells though meiosis in the sperm cells. A spermatocyte is a cell that can produce other sperm cells. The spermatozoa is a single cell which can fertilize the ovum.
Epigenetic
An epigenetic trait is a phenotype resulting from change in the chromosome without altering the DNA sequence. Affected by outside factors.
Polygenetic
A polygenetic trait is a trait influences by one or more genes. (height or skin color)
Multifactorial
When more than one factor causes a trait.
Pleiotrophy
When one locus affects more than one phenotypic trait.
