7A - 7B Genetics Flashcards
eoxyribonucleic acid (DNA)
a double-stranded nucleic acid chain made up of nucleotides. DNA carries the instructions for proteins which are required for cell and organism survival.
Nucleotide
the monomer unit of nucleic acids. Made up of a nitrogen-containing base, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a phosphate group.
Gene
a section of DNA that carries the code to make a protein.
Genome
the complete set of DNA contained within the haploid set of an organism’s chromosomes.
Allele
alternate forms of a gene.
Locus (pl. loci)
the fixed position on a chromosome where a particular gene is located.
What is DNA
-forms the major component of chromosomes and contains coded genetic instructions.
-It is formed by the continuous pairing of base pairs into a longer, double-stranded nucleic acid chain.
What is nucleotide made up of
A deoxyribose sugar
A phosphate group
A nitrogen-containing base
Nitrogen-containing bases
-Four different kinds of nucleotides are found in DNA.
The four bases in DNA are
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
From DNA to genes
-gene is a particular section of DNA that codes for the creation of an individual polypeptide chain (protein)
-a cell will then read to make the proteins required for a range of cellular functions.
-The order of bases in the double helix determines which protein gets made
What is a genome?
-Each person has two copies of each gene, one inherited from their mother and the other from their father.
-This collection of genes is called your genome,
-houses all of the genetic information needed to build and maintain you: a complex organism.
-roughly 25 000 different genes inside each of your cells.
Alleles
Alleles are different forms of the same gene but with small differences in their base sequence.
Histone protein
highly basic proteins that associate with DNA inside the nucleus and help it condense into a chromosome allowing it to fit inside the nucleus.
Chromosome
the structure made of protein and nucleic acids that carries genetic information
Somatic cell
any cell that is not a reproductive cell (such as sperm and egg cells). Somatic cells are diploid (2n), meaning they contain two sets of chromosomes – one inherited from each parent
Chromatid
one half of a replicated chromosome. Prior to cell division, chromosomes are duplicated and two copies join together at their centromeres (joined chromatids are known as sister chromatids).
Homologue
a homologous chromosome.
What is a chromosome?
-An organism’s genome sits inside the nucleus of each of their somatic cells in the form of DNA.
-Each molecule of DNA is coiled tightly around histone proteins and packaged into thread-like structures called chromosomes.
-Human somatic cells usually contain 46 chromosomes.
-Chromosomes vary in size depending on the number of nucleotides they contain.
Diploid (2n)
full set of chromosomes contained within an organism. Two copies of each chromosome. Human somatic cells have 46 chromosomes (2n = 46)
Haploid (n):
having one copy of each chromosome. A set of unpaired chromosomes. Human gametes (eggs & sperm) have 23 chromosomes
Homologous chromosomes
We call each of the sets of 23 chromosomes within a human nucleus a pair of homologous chromosomes
Criteria for homologous chromosomes
They are the same in size and length
They have the same centromere position
They share the same genes at the same gene loci
Karyotypes: visualising chromosomes
-A karyotype is a visual representation of an individual’s entire genome organised into homologous pairs.
-Chromosomes are arranged by size and centromere position into their homologous pairs.
Autosome
any chromosome in humans that is not a sex chromosome
Sex chromosome
a chromosome responsible for determining the biological sex of an organism.
Aneuploidy
Aneuploidy refers to a chromosomal abnormality in which an organism possesses an incorrect number of total chromosomes caused by the addition or loss of an individual chromosome
Monosomy
if an organism has one missing chromosome (2n - 1)
Trisomy
if an organism has one extra chromosome (2n + 1)
Tetrasomy
if an organism has two extra chromosomes (2n + 2)
Polyploidy
-a chromosomal abnormality in which an organism has more than two sets of each chromosome
-(2n = 46), the individual would be 3n = 72 or more.
-quite common for other organisms, especially plants,
