Topic 9 - DNA and Inheritance Flashcards
What is a genome?
The genome is the entire genetic material of an organism.
What is DNA?
DNA is a double-helix polymer, which means it is a polymer made up of two strands forming a twisted, ladder shape.
What is a gene?
A gene is a small section of DNA that codes for a sequence of amino acids, which combine to give a specific protein.
What is a chromosome?
Long strands of DNA are coiled up to form chromosomes containing many genes.
What is a nucleotide?
Units that repeat throughout the structure of DNA are called nucleotides. Each of these is made up of a sugar, with a phosphate and a base attached to the sugar.
What is a polymer?
A large, chain-like molecule, extending for hundreds or thousands of atoms joined by strong covalent bonds.
What are the 4 bases?
Thymine - Adenine
Guanine - Cytosine
How is DNA held together?
By the attractions between 2 opposite bases
Which part of DNA do the sugar and phosphate make up?
The long strands
What is a codon?
A specific sequence of three bases that codes for a specific amino acid. This is known as the ‘triplet code’.
What significance does the order of the bases have in protein synthesis?
The order of the bases on the DNA tells us the order for combining amino acids to create particular proteins.
How are different proteins made?
The protein made by a gene is different because each gene has a different sequence of bases.
What is a ‘DNA fingerprint’?
Each person has a unique set of chromosomes which can be used to identify them using genetic profiling.
Genetic Profiling Step 1
Isolation - DNA from an individual is taken (e.g. through a cheek swab) and extracted from the cell’s nucleus.
Genetic Profiling Step 2
Fragmentation - Chromosomes are broken up into shorter segments of DNA.
Genetic Profiling Step 3
Separation - Using electrophoresis, whereby an electric current is passed through gel, the fragments of DNA are separated out according to size.
Genetic Profiling Step 4
Comparison - The fragments of DNA can then be compared to other DNA fingerprints to work out whether two DNA fingerprints are the same, or to identify whether certain genes are present.
What can genetic profiling be used for?
Identifying disease genes, classifying species, solving crimes and paternity tests.
How can genetic profiling be used to identify disease genes?
Comparing band patterns from different patients with the same genetic disease shows which genes the patients have in common, which helps identify genes linked to genetic disorders.
How can genetic profiling be used to classify species?
Comparing band patterns of different species shows scientists how closely related different species are (in terms of evolution), which helps them classify species.
How can genetic profiling be used to solve crimes?
Comparing band patterns of any DNA found at a crime scene (e.g. from blood) with that of the victim and with different suspects can place suspects at the scene of the crime.
How can genetic profiling be used to test paternity?
Comparing the band patterns from a child with that of its mother and with possible fathers, and discounting the genes inherited from the mother, it can be worked out which DNA came from the father.
What are alleles?
Alleles are different forms of the same gene
How are characteristics determined?
Humans have pairs of every gene and in one gene, each half of the pair may have different alleles. People’s characteristics are determined by the alleles that they have.
What is a dominant allele?
A dominant allele is always expressed, regardless of the identity of the other allele. It is represented by a capital letter.
What is a recessive allele?
A recessive allele is only expressed if the other allele is also recessive. It is represented by a lowercase letter.
What is the phenotype?
A phenotype is an observed characteristic of an individual, determined by the interaction between the genotype and environment.
What is the genotype?
Genotype refers to the combination of alleles an organism has.
What does heterozygous mean?
A person with two different alleles (Bb)
What does homozygous mean?
A person with two of the same alleles, homozygous recessive (bb) or homozygous dominant (BB).
What is a monohybrid cross?
When the inheritance of traits is determined by a single gene.
What kind of diagram can be used to show monohybrid crosses?
Punnett Squares
Where are the parents’ genes drawn on a Punnett Square?
Along the top and left side, the possible offspring are then filled in on the grid.
What are parents called on a Punnett Square?
F0 generation
What are the offspring called on a Punnett Square?
F1 generation
What would the offspring’s offspring be called on a Punnett Square?
F2 generation
What else can Punnett Squares represent?
Selfing, where plants pollinate themselves; the plant is both ‘parents’.
What are the sex chromosomes of a female?
Females are XX, so an egg contains one X chromosome.
What are the sex chromosomes of a male?
Males are XY, so a sperm contains either one X or one Y chromosome.
What is genetic engineering?
Genetic engineering involves changing the genetic material of an organism by removing, changing or inserting individual genes from another source to produce the desired characteristic.
What can genetic engineering be used for?
Inserting genes into crop plants to provide additional vitamins, into bacteria to produce human insulin, into crop plants to give them resistance to herbicides or insects.
What are the advantages of genetic engineering?
Preventing inherited diseases, improving food production efficiency due to increased yields, providing missing nutrients, no complications so far.
What are the disadvantages of genetic engineering?
Negatively impact wild flower and insect populations i.e. ‘superweed’, thus reducing biodiversity, long-term effects on human health, unethical to create new life.
What does GM stand for?
Genetically modified
What is a permanent change in the nucleotide sequence of DNA called?
A mutation
