Topic 6: Inheritance, Variation and Evolution Flashcards
What is mitosis?
A type of nuclear division that gives rise to cells that are genetically identical
Mitosis is used for growth, repair of damaged tissues, replacement of cells, and asexual reproduction.
What is meiosis?
A type of nuclear division that gives rise to cells that are genetically different
Meiosis is used to produce gametes (sex cells).
What is sexual reproduction?
A process involving the fusion of the nuclei of two gametes to form a zygote
It results in offspring that are genetically different from each other.
What are the gametes of animals?
Sperm cells and egg cells
What are the gametes of flowering plants?
Pollen cells and egg cells
Define fertilisation.
The fusion of gamete nuclei
This results in variation in the offspring as each gamete comes from a different parent.
What is asexual reproduction?
A process that does not involve sex cells or fertilisation
The offspring are genetically identical to the parent.
What is the main type of cell division involved in asexual reproduction?
Mitosis
What is the chromosome number in gametes after meiosis?
Haploid
This means they have half the normal number of chromosomes.
How many haploid daughter cells are produced at the end of meiosis?
Four
What is the importance of meiosis?
Produces gametes and increases genetic variation of offspring
Variation occurs due to new combinations of maternal and paternal chromosomes.
What happens during fertilisation?
Male and female gametes fuse to become a zygote
The zygote contains the full number of chromosomes.
What is cell differentiation?
The process of cells becoming specialised to perform particular functions
What is an advantage of sexual reproduction?
Increases genetic variation
What is a disadvantage of sexual reproduction?
Takes time and energy to find mates
What is an advantage of asexual reproduction?
The population can be increased rapidly when conditions are right
What is a disadvantage of asexual reproduction?
Limited genetic variation in the population
How do some organisms reproduce depending on circumstances?
Some reproduce by both methods: sexually and asexually
What is the genome?
The entire set of the genetic material of an organism
What is DNA?
Deoxyribonucleic acid, the molecule that contains instructions for growth and development
What is the structure of DNA?
A polymer made up of two strands forming a double helix
What are chromosomes?
Structures located in the nucleus of cells that contain DNA
What is a gene?
A short length of DNA found on a chromosome
What does each gene code for?
A particular sequence of amino acids
What was the Human Genome Project?
An international collaborative research effort to determine the DNA sequence of the entire human genome
What are nucleotides?
The individual subunits of DNA
What are the four different bases in DNA?
- Adenine (A)
- Cytosine (C)
- Thymine (T)
- Guanine (G)
What is complementary base pairing?
Adenine pairs with Thymine (A-T) and Cytosine pairs with Guanine (C-G)
What is the role of ribosomes in protein synthesis?
Ribosomes use the sequence of bases to make proteins
What is mRNA?
Messenger RNA that carries the code from DNA to ribosomes
How is a change in DNA structure significant?
It may result in a change in the protein synthesized by a gene
What does the ribosome read during protein synthesis?
The code on the mRNA in groups of three bases
What is the function of ribosomes in protein synthesis?
Ribosomes read the code on the mRNA in groups of three and translate it into a sequence of amino acids.
What does each triplet of bases in mRNA code for?
Each triplet of bases codes for a specific amino acid.
What happens to the amino acid chain once it is assembled by the ribosome?
It is released from the ribosome to fold and form the final structure of the protein.
What is the unique shape of a protein important for?
The unique shape enables proteins to fulfill specific functions.
What are enzymes?
Proteins that act as biological catalysts to speed up chemical reactions.
What are hormones?
Proteins that carry messages around the body.
What are structural proteins?
Proteins that provide structure and are physically strong.
Define mutations in the context of genetics.
Random changes that occur in the sequence of DNA bases in a gene or chromosome.
What can mutations in a gene lead to?
Changes in the protein that the gene codes for.
What is an insertion mutation?
A mutation where a new base is randomly inserted into the DNA sequence.
What is a deletion mutation?
A mutation where a base is randomly deleted from the DNA sequence.
What is a substitution mutation?
A mutation where a base in the DNA sequence is randomly swapped for a different base.
True or False: Most mutations significantly alter the protein function.
False.
What can happen if the shape of the active site on an enzyme changes?
The substrate may no longer be able to bind to the active site.
What is gene switching?
The process by which non-coding parts of DNA can switch genes on and off.
What is monohybrid inheritance?
The inheritance of characteristics controlled by a single gene.
What is a phenotype?
The observable characteristics of an organism.
What is a genotype?
The combination of alleles that control each characteristic.
Define dominant allele.
An allele that only needs to be inherited from one parent for the characteristic to show in the phenotype.
Define recessive allele.
An allele that needs to be inherited from both parents for the characteristic to show in the phenotype.
What does homozygous mean?
Having two copies of the same allele.
What does heterozygous mean?
Having two different alleles for a gene.
What is polygenic inheritance?
Inheritance of characteristics controlled by more than one gene.
What is a Punnett square used for?
To show the possible combinations of alleles that could be produced in the offspring.
How is a family tree diagram used in genetics?
To trace the pattern of inheritance of a specific characteristic through generations.
What do males and females represent in a family tree diagram?
Males are squares and females are circles.
What is the probability of offspring being tall in a monohybrid cross with a 3:1 ratio?
75%.
What is the probability of offspring being short in a monohybrid cross with a 3:1 ratio?
25%.
What type of disorders are caused by the inheritance of certain alleles?
Inherited disorders.
Fill in the blank: A ________ is a protein that acts as a biological catalyst.
enzyme
Fill in the blank: Characteristics controlled by more than one gene are described as ________.
polygenic
Fill in the blank: The combination of alleles that control each characteristic is called the ________.
genotype
What is the probability of an offspring being tall?
75%
What is the probability of an offspring being short?
25%
What are inherited disorders caused by?
Inheritance of certain alleles
Name one example of a genetic disorder that can be inherited.
Cystic fibrosis
What is cystic fibrosis?
A genetic disorder of cell membranes causing thick, sticky mucus
What is the allele responsible for cystic fibrosis?
Recessive allele (f)
What must individuals be to have cystic fibrosis?
Homozygous recessive (two copies of the recessive allele)
If both parents are carriers of cystic fibrosis, what is the chance of producing a child with the disorder?
1 in 4 or 25%
If only one parent is a carrier of cystic fibrosis, what is the chance of producing a child with the disorder?
No chance
What is polydactyly?
A genetic disorder causing extra fingers or toes
What type of allele causes polydactyly?
Dominant allele (D)
True or False: A child can inherit polydactyly if only one parent is a carrier.
True
What is in vitro fertilization (IVF)?
Process of fertilizing embryos in a lab and implanting them into the mother’s womb
What can be analyzed from an embryo before implantation?
Its genes
What is one concern regarding embryo screening?
Potential destruction of embryos with genetic disorders
What is gene therapy?
Inserting normal alleles into chromosomes of individuals with defective alleles
True or False: Gene therapy is always successful.
False
What are the sex chromosomes in females?
XX
What are the sex chromosomes in males?
XY
How many pairs of chromosomes do ordinary human body cells contain?
23 pairs
What do 22 pairs of chromosomes control?
Characteristics only
What are the ethical concerns associated with embryo screening?
Destruction of potential life and premature termination of pregnancy
Fill in the blank: Cystic fibrosis is caused by a ______ allele.
recessive
Fill in the blank: Polydactyly is caused by a ______ allele.
dominant
