Unit 4 Topic 1 - DNA Flashcards
What 3 components make up a nucleotide?
A phosphate, a sugar and a nitrogen base
What number carbon is the P group attached to?
5th carbon
What are the complementary base pairs?
Adenine - Thymine
Guanine - Cytosine
Explain the composition of chromosomes
Consists of DNA strands coiled around histone proteins to create a supercoil
What are the stages of Mitosis
prophase, metaphase, anaphase, telophase, cytokinesis
List and explain the three steps of DNA replication.
- The enzyme helicase ‘unzips’ the DNA to create a fork
- the enzyme DNA polymerase adds nucleotides to the template strands to built two new complementary strands.
- two identical DNA helices are produced
Explain the difference between sister chromatids and homologous chromosomes
Sister chromatids refer to each half of a chromosome, whereas homologous chromosomes refer to an inherited pair of chromosomes
What are the phases of meiosis?
Interphase, prophase, metaphase, anaphase, telophase, cytokinesis
How many chromosomes do each haploid cell have after meiosis?
23
What is spermatogenesis?
the production of sperm in the testes
how many haploid sperm cells are produced after meiosis
4
What is Oogenesis
The production of ovaries in females
How many viable haploid cells are produced in Oogenesis
1, The other three become polar bodies
When do the stages of Oogenesis occur in women?
Mitosis -> before birth
Meiosis 1 -> at puberty
Meiosis 2 -> at pregnancy
Identify the key differences between spermatogenesis and oogenesis
Spermatogenesis produced 4 viable haploid cells, Oogenesis only produces 1.
Spermatogenesis is a constant process that begins at puberty, whereas Oogenesis is a discontinuous process.
What is independent assortment
the orientation of chromosomes during metaphase is random, contributing to genetic variation
what is random feralization
The random chance of any sperm and egg fertilizing, resulting in random variation
What is a gene
a sequence of nucleotides that code for a gene product
What is a genome
the complete set of genetic material in an organism
What makes up a codon
3 nucleotides
What is a gene’s coding region called
exon
what is a gene’s non-coding region called.
intron
note: It is unclear what the exact purpose of these regions is but they may aid in gene regulation
List the 4 features of a gene’s structure
start and stop codons
promoter region
exon
intron
What is the code for a start codon
ATG (which becomes AUG, codes for methionine)
What is a promoter region
A TATAAA sequence where the RNA polymerase binds to start transcription.
What is an exons role?
they are used to make RNA or proteins
Define transcription
the synthesis of mRNA from DNA
List and define the 3 steps of transcription
Initiation - RNA polymerase binds to the promoter region and breaks the hydrogen bonds causing DNA strands to separate
Elongation - RNA polymerase moves along the gene creating an RNA strand from complementary nucleotides
Termination - RNA polymerase reaches the stop codon which causes the RNA to detach
What is translation
The process in which mRNA is read and used to build a chain of amino acids (polypeptide chain)
What is the role of transfer RNA (tRNA)
tRNA adds the specific amino acid to the polypeptide chain
Thymine is replaced with what base in RNA?
Uracil
List and define the stages of translation
Initiation - Ribosome assembles around mRNA and the first tRNA is put in place.
Elongation - mRNA is read and amino acids are added into the polypeptide chain
Termination - finished protein chain is released
What is the purpose of gene expression
To produce a functional gene product
What is a transcription factor
Proteins that control gene expression
What are epigenetics
environmental mechanisms that alter gene expression without directly involving the DNA sequence
(mechanisms can include diet or pollutants)
Explain the difference between incomplete dominance and codominance
Incomplete dominance results in a blended phenotype (e.g. a red and white flower may produce a pink flower)
Codominance results in both parents phenotypes being represented
What is a Polymerase Chain Reaction
The replication of a single or few copies of DNA into millions or billions of copies so that the DNA can be amplified and studied
