Topic 1: DNA, Genes, The Continuity of Life Flashcards
define organelle
a membrane bound compartment in a cell that performs a specialised function
name the general features of prokaryotes
- lack distinct nucleus
- no membrane-enclosed organelles
- contain free floating ribosomes
name the general features of eukaryotes
-distinct nucleus
- contain membrane-bound organelles
- contain ribosomes
describe DNA in prokaryotes
a single circular chromosomes and plasmids
define intron
a segment of DNA or RNA molecule that doesn’t code for proteins and interrupts the sequence of genes
where is DNA found in prokaryotes
found in the nucleoid region
where is DNA found in eukaryotes
found in the nucleus
define mitochondria
organelle in both eukaryotic cells (heterotrophs and autotrophs), site of cellular respiration
explain mitochondrial DNA (mDNA)
a double stranded, circular molecule with no introns
recall the basic structure of DNA
- carried hereditary info
- a double helix structure with two complementary strands
- nucleotides are the building blocks of DNA/RNA
what are nucleotides
a group of molecules that, when linked together, form the building blocks of DNA/RNA
what are nucleotides made of
a deoxyribose sugar, a phosphate group, a nitrogenous base
what are the 4 dif types of nitrogenous bases in nucleotides
Adenine and Thymine
Guanine and Cytosine
(Thymine is only found in DNA, in RNA it is replaced by Uricil)
whats the dif between maternal and paternal
maternal - from mother
paternal - from father
define diploid
cell containing 2 complete sets of chromosomes - one from each parent
define haploid
cell having a single set of unpaired chromosomes, usually a gamete (sex cell)
what are homologous chromosomes
- have one paternal and one maternal, containing the same genes (the sex genes)
define autosomal chromosomes
chroms. not related to gender/ sex (chromosomes 1 to 22)
what are the differences between make and female when it comes to chromosomes 23
- females have two homologous pairs of X chromosomes
- males have one X and a shorter Y chromosomes
what is a human karyotype
an individual’s complete set of chromosomes
define gene
segment of DNA that codes for a specific phenotypic trait
define allele
the different variations of a gene
define gene locus
a fixed positions on a chromosomes where a specific gene is found (location)
homozygous?
same alleles (AA)
heterozygous
different alleles (Aa)
are all homologous chromosomes the same
they contain the same genes, however they are not identical due to the variations between alleles
explain meiosis
cell division that results in 4 genetically unique daughter cells - which have half the number of chromosomes (haploid) of the parent cell (diploid)
basic process of cellular division:
meiosis i –> go from one parent cell to two daughter cells
- two daughter cells then undergo a new cellular division, resulting in each of those forming two new daughter cells themselves
what are spermatogenesis and oogenesis
the processes of male and female gamete production (spermatogenesis - sperm)
define fertilisation
the union of male and female gametes to product a zygote: the first diploid cell of a new organism
define genome
all the genetic material in the chromosomes of an organism - basically the complete DNA sequences of an organism
explain non-coding DNA
- majority of human DNA is non-coding - plays important role in gene activity (determine when and where genes are turned on and off)
what are examples of non-coding DNA
centromeres, telomeres, introns, etc
define amino acid
the building blocks of proteins - protein structure is determined by the sequence and folding of these amino acids
define transcription
process by which complementary copy (mRNA) of a gene (DNA) is made in the nucleus
define translation
process by which an mRNA sequence is converted into a specific sequence of amino acids (carried by tRNA) in the ribosomes
define messenger RNA (mRNA)
single stranded nucleic acid - carried protein info from the DNA in a cell’s nucleus to the cell’s cytoplasm
define transfer RNA (tRNA)
small RNA molecule that transfers specific amino acids to the ribosome during formation of proteins
define codon
set of three nitrogen bases in mRNA
define anticodon
complementary set of three nitrogen bases in tRNA
where does transcription occur
nucleus
where does RNA processing occur
nucleus
where does translation occur
ribosomes
explain gene expression
process by which the info stored in a gene is used to synthesize a functional gene product
define enzymes
speeds up the reactions by lowering the activation energy required
what is gene regulation
the process of controlling which genes are expressed by which cells
define mutation
permanent change in the nucleotide sequence of DNA (essential for evolution)
what is a point mutation
occurs when a single nucleotide base is changed, inserted or deleted from a sequence
a point mutation can cause a frameshift - explain
the error in the DNA sequence carried through the transcription and translation process
define mutagen
a physical, chemical or biological agent that causes mutations
explain physical mutagens
breaks chemical bonds and damage DNA (e.g. include ionizing radiation (some UV, X-rays))
explain biological mutagen
cause mutations by inserting their own DNA into the human genome in cell division
explain non-disjunction mutations
occur when homologous chromosomes or sister chromatids fail to separate properly during cell division –>result: daughter cells have incorrect no. of chromosomes (aneuploidy)
explain trisomy
type of aneuploidy (an abnormality in the number of chromosomes in a cell) where there are 3 chromosomes instead of the normal two for a particular homologous pair –> trisomy 21 = down syndrome
what are somatic cells
any cell other than the reproductive cells (e.g. muscle cells)
how to inherited mutations alter the variations in genotype of offspring..
they introduce new alleles into the gene pool, and therefore increase variation within the genotypes of the population
what is a sex linked allele
one that is carried on one of the sex chromosomes (most often X - as it contains more genetic info)
what is polygenic inheritance
refers to phenotypic traits that are determined by two or more genes (e.g. skin, eye colour, height)
what is recombinant DNA
the result of combining the DNA of two dif. species
describe the process of making recombinant DNA
- a gene is isolated from a target organism
- its inserted into a bacterial plasmid, which is then inserted back into the bacteria
- the bacteria pop. is grown in a culture where it produces the protein products of the inserted gene
what is a plasmid
small circular DNA strand found in prokaryotic cells - replicate independently of chromosomes
what are restriction enzymes
DNA sequences are cut at specific nucleotide sequences called recognition sites - this enzyme moves along the length of the DNA, cutting it each time a recognition site is passed
what are DNA ligases
responsible for joining DNA (or RNA) fragments together
what is DNA sequencing
- process of determining the precise order of nucleotides within a segment of DNA
- determining the order of adenine, guanine,etc
what can DNA profiles be used for
- confirm how closely related individuals are
- trace inheritance patterns
- solve crimes
what is a polymerase chain reaction (PCR)
- DNA samples are usually quite small
- so, before they can be analysed, samples must be amplified
- polymerase enzymes catalyse and expotentially amplify copies of a specific sequence
explain gel electrophoresis
- a lab technique used to separate mixtures of DNA based on molecular size
