DNA, Genes, Cell Division Flashcards
How many alleles are in a sector of genes?
2 alleles
What are genes?
A sector of code that lies in the DNA. It contains alleles that determine the physical attributes of a person.
What is non-mendelian?
Recessive
What is mendelian?
Dominant
What sex can be a carrier for x-linked diseases?
Female as they have two X chromosomes
What sex chromosomes do males have?
X Y
What sex chromosomes do females have?
X X
What is inheritance?
The passing down of physical traits through a family line. Characteristics come from parents
What do we call the passing of traits?
Heredity
What type of cell division allows for traits to be passed down?
Meiosis, but can also be through mitosis
How do we represent dominant traits?
A capital letter, eg. GG
How do we represent recessive traits?
A lowercase letter, eg. gg
What are the two types of genetic inheritance?
Dominant and Recessive
What is a recessive trait?
A characteristic that will ONLY show is both lowercase letters are shown. Example: gg will show the recessive gene, but gG will show dominate (even though there is a recessive) as dominant dominates overall.
What is a dominant trait?
A characteristic that will always show is presented in the allele. Example: Gg will show a dominant trait as G overpowers g.
GG is also dominant
Describe a genotype
The genes given to the offspring, the letters given to represent them (eg. gg)
How do you write out a genotype?
Use the letters, so either GG, gg, Gg, gG
Describe a phenotype
The physical appearance expressed in the offspring.
How do you write a phenotype?
Refer to specific physical attributes.
EXAMPLE: Red hair = 25%
Brown = 75%
What is heterozygous?
Having two different alleles = one dominant and one recessive (one uppercase and one lowercase)
What is homozygous?
Two of the same alleles = two dominant or two recessives (eg. AA or aa)
What is a hereditary carrier?
An organism that has inherited a recessive allele from a parent for a trait or mutation. It is not typically shown in the carrier organism, but its offspring may inherit that trait.
Define DNA
Organic material is found in the cells of most living things. It is the genetic code for an organism and gives information on an organism’s traits.
How do you spell DNA?
Deoxyribonucleic Acid
Who theorized the structure of DNA?
Watson & Crick
What is the modern model of DNA called?
Double Helix structure
What are things that can be inherited from a parent?
Alleles, genetic disorders, traits, characteristics eg. height
How many backbones are in the double helix model?
2
What are DNA’s backbones made of?
Sugar-phosphate
Where in the cell is DNA located?
Nucleus
What is a nucleotide?
Organic molecules in DNA. They are a repeating sequence made of sugar, phosphate, and nitrogen
What are base pairs?
Complimentary pairs, bonded by hydrogen, are found in genes. They form DNA’s building blocks and hold the structure together. They are nitrogenous bases.
What pairs with adenine?
Thymine
What pairs with guanine?
Cytosine
What pairs with thymine?
Adenine
What pairs with cytosine?
Guanine
Why are base pairs bonded by hydrogen?
As it is weak, it allows DNA to replicate
What type of chemical bond joins the two DNA bases?
Hydrogen
Which nucleotide parts make up the outside of the DNA?
Sugar, phosphate
Which nucleotide parts make up the inside of the DNA?
Nitrogen
How many chromosomes does a human have, and what are they?
23 total pairs, 46 induvidual. 22 pairs of autosomes and 1 pair of sex (X, Y) chromosomes.
What is the acronym for cell division?
IPMAT+C
What is mitosis?
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. Reproduction, repair, and growth
Why is mitosis important?
Without it, dead cells would never be replaced, organisms would never grow or heal.
What is meiosis?
2 rounds of cell division, ending up with half the amount of DNA as it is half from each parent. Meiosis can introduce genetic variation, important as it creates diversity in the population
What is unique about homologous chromosomes?
Homologous chromosomes can swap parts to look different (random process)
What is a haploid cell?
The daughter cells of meiosis (half set of DNA)
Define a diploid cell
The daughter cells of mitosis (full set of DNA)
Why must haploid cells have half the amount of DNA?
If egg and sperm have two full sets, then there is too much DNA. Otherwise, mutations can occur.
What is a chromosome?
An X structure is made of DNA. They allow DNA to be accurately replicated.
What is a homologous chromosome?
Two chromosomes in a pair, one from mother and one from father.
Define a chromatid
The single strand of a chromosome
What are chromosomes made up of?
DNA tightly coiled many times around proteins called histones
Define sister chromatids
The two chromatids are in the same chromosome.
Define a centromere
Part of the chromosome where spindles attach.
What is the role of meiosis?
To introduce genetic diversity
Describe interphase
Pre-mitosis where DNA replication occurs
Describe prophase
Prophase prepares the cell for division. Parent cell begins to break the nucleus down, chromosomes become visible and organised
Describe metaphase
Chromosomes line up in the middle of the cell to allow them to separate to opposite ends of the cell. Chromatids prepare to be broken apart and spindle fibres come out of centrioles and attach, preparing to separate the chromosomes.
Describe anaphase
Sister chromatids (previously a chromosome) separate due to spindle fibres pulling them apart. Chromatids separated to opposite ends of the cell
Describe telophase
- Daughter cells that are formed are beginning to separate
- Nucleus reforms in each cell around DNA
- Not completely separated
- Centrioles disappear
Describe cytokinesis
- Daughter cells separate fully
- DNA disorganises and is no longer visible
What is a centriole?
Organisims inside a cell that aid organisation
What is a zygote?
A fertilized cell
What is a gamete?
The reproductive cell of an animal or a plant
Define a somatic cell
Any cells in the body that are not involved in reproduction. They are diploid cells that contain 46 chromosomes arranged in 23 pairs, 22 autosomes and 1 sex chromosome (e.g xy, xx)
Define a gamete cell
Reproductive cells such as sperm or egg. They are haploid and contain no pairs
What is a sex chromosome
Determine sex of a person, are one pair e.g XY or XX
Define autosome
A chromosome that isn’t used to determine the sex of someone. There are 22 pairs of autosomes in a cell. The other pair is a sex cell
Where are alleles found?
On a chromosome
What is an allele?
A variant of a gene for a trait. They are located in chromosomes and there are two alleles per sector of gene.
What is natural selection?
It is a mechanism of evolution. It “chooses” which organisms can survive based on their phenotype and genotype. It occurs randomly but follows a pattern in which it wipes out.
What is artificial selection?
The identification, by humans, of desirable traits. This might include fast running or good vision. Humans may choose to breed these traits down generations, “weeding” out those inferior.
What is a mutation?
An alteration in the genetic sequence that varies an organism’s phenotype.
What can cause mutations?
Fluctuations in weather, UV radiation, chemical exposure
What is an abiotic factor?
Non-living, physical, or chemical aspects of environment eg. bushfires, rain, temperature.
What is a biotic factor?
Living pressures eg. predators, algae, snakes
How can organisms adapt?
As the population changes, genetic traits will appear more commonly in organisms. These traits have been passed down generations as they have allowed the previous to survive. The next generation takes these traits among others to adapt to their surrounding environment.
