4. Genetics Flashcards
(37 cards)
What are genetics and characteristics?
Genetics are a unit of hereditary characteristics, which are fixed from the moment of fertilisation. However acquired characteristics occur later (ie scars and skills)
What is variation in characteristics?
Continuous variation is when there are many intermediate forms between two extremes (ie. height)
Discontinuous variation are characteristics that show few or no intermediate forms (ie tongue rolling)
What is mitosis and what is its function?
Mitosis is the process of cellular asexual reproduction, in which the nucleus divides to form two new nuclei.
Three reasons cells reproduce by asexual reproduction is for;
- growth
- repair
- replacement
What is interphase?
Interphase occurs before mitosis in preparation for the mitosis cycle. The cellular organelles double, the DNA replicates and protein synthesis occurs
What are the phases in the Mitosis Cycle?
- Prophase - chromatin (DNA + proteins) in the nucleus condense
- Metaphase - the chromosomes gather in the middle of the cell, ready to divide
- Anaphase - the chromatids of each chromosome separate and are pulled towards the poles
- Telophase - small nuclear vesicles in the cell begin to reform around the groups of chromosomes at each end
- Cytokinesis - the cytoplasm divides and daughter cells form
What are the main differences between mitosis and meiosis?
- mitosis produces genetically identical cells, while meiosis produces unique cells
- mitosis produces diploid cells, meiosis produces haploid cells
- mitosis occurs throughout an organism’s life, but meiosis only occurs at certain times
- mitosis is involved in asexual reproduction, meiosis is involved with sexual reproduction
What is meiosis?
The formation of gametes through sexual reproduction. Sex cells have 23 chromosomes each (haploid number), arranged into 23 homologous pairs
Provide definitions for the following terms;
- loci
- alleles
- the position of a gene on a chromosome
- different expressions of the same gene
Genes that occupy the same locus of homologous chromosomes are alleles of each other
What are genes?
Genes code for the biological development and growth of organisms. Genes are made up of deoxyribonucleic acid (DNA).
What is DNA? What is it made up of?
Deoxyribonucleic acid, a long thread-like molecule that contains the genetic instructions for an organisms development.
DNA consists of a sugar phosphate backbone made up of deoxyribose sugar and phosphates. Connected to the deoxyribose sugar are nitrogenous bases. A nucleotide is made up from once sugar, one phosphate and one base.
What is the pairing rule?
Only certain nitrogenous bases can pair with each other, purines can only bind with pyrimidine
Adenine (purine) is opposite Thymine (pyrimidine)
Guanine (purine) is opposite Cytosine (pyrimidine)
What is a codon?
A codon is a group of three chemical bases that form the DNA. In the arrangement of these bases is the instructions for an amino acid, and a protein from that amino acid
What are introns and exons?
Introns separate the coding and ‘non-coding’ DNA in eukaryotic DNA.
Exons code for protein, and thus determine an organism’s traits
What is the process of transcription?
The process in which DNA codes for messenger RNA. Initially, the whole gene is turned into mRNA, including the introns, which is called pre mRNA.
Next the introns are removed in a process called splicing, where the exons then join together to form the processed mRNA. This molecule than codes for proteins through the translation process.
How do scientists determine the coding sections of DNA?
Scientists work backwards from proteins to identify the mRNA that codes for it. Once they determine the mRNA sequence, they can make complementary DNA which is made up of exons. They then compare this to the DNA to find the matching gene
What is non-coding DNA?
Although scientists do not yet know the function of non-coding DNA, it significantly differs between individuals (ie fingerprinting)
Some of the non-coding DNA can be transcribed however, such as introns and functional RNA which contributes to protein synthesis
What is a mutation?
The change in genetic material of an organism, usually in the DNA
A permanent change in the genetic code of a cell
How do you know if a mutation can be passed onto offspring?
If a mutation occurs in the gamete, it can be passed onto the offspring of the affected individual. It it occurs in somatic cells (body cells), it cannot be inherited
What is the difference between spontaneous and induced mutations?
Induced mutations are caused by environmental factors (ie radiation), whereas spontaneous mutation are the result of random mistakes in DNA replication
What’s the difference between positive, negative and neutral mutations?
Positive mutations: causes a change that is beneficial
Neutral mutations: has no impact on the phenotype
Negative mutations: changes that endanger the organisms survival
What are block mutations?
Mutations where parts of the chromosomes are deleted, repeated or translocated to other chromosomes, which impacts the alleles
What are these mutations?
- when one chromosome is present in an abnormal number of copes
- when the chromosome number doubles
- aneuploidy (eg Down Syndrome)
- Polypoids
What are the 4 types of chromosomal structural changes?
- deletion: part of a chromosome or DNA sequence is left out during DNA replication
- inversion: a segment of a chromosome is reversed end to end
- translocation: unusual rearrangements of chromosomes
- duplication: production of one or more chromosomes or DNA pieces
What is crossing over?
Occurs in prophase 1, when the two chromosomes of a homologous pair exchange equal segments with each other
