Cells And DNA Flashcards
Where in a cell would you find DNA?
The nucleus of cells for plants, animals and fungi.
Name the parts of the DNA molecule.
Strand
Backbone
Nucleotide
Sugar group
Phosphate group
Base: A, C, G or T
Give a short description of the structure of DNA
DNA is a double stranded molecule that is made up of sugar, phosphate and four bases, A, C, G or T. The sugar and phosphate make up the backbones of each strand, while the bases are fojj uh no in the middle of the molecule. The base Adenine (A) always pairs with the base thymine (T), while the base guanine (G) always pairs with cytosine (C). A nucleotide is a collection of one phosphate, one sugar and one base. Nucleotides are the building blocks of the DNA molecule.
What is a chromosome?
A chromosome is a long strand of tightly wound DNA found in the nucleus of the cell.
How many DNA molecules make up one chromosome?
There is one DNA molecule per chromosome
What are homologous chromosomes?
Homologous chromosomes are chromosomes that are very similar and pair during cell division. They have the same genes, in the same order, all the way down, but may have different alleles.
Explain the difference between a body cell (somatic cell) and a sex cell ( gamete) in terms of:
a. Purpose
b. Where you would find each type of cell in the human body
Most of a multicellular organism’s body is made up of somatic cells (body cells). Body cells are the building blocks of your skin, muscles, heart etc. These make up the major tissue and organ systems of the body and help to keep the organism itself alive. Somatic cells are referred to as diploid, meaning there are pairs of chromosomes within the cell.
Sex cells (gametes) are specific kinds of cell an organism produces in order to reproduce (make offspring). Gametes are usually produced in specific organs, such as the ovaries or testes of mammals, or in the flowers of plants. They are used to make the next generation of the organism. Gametic cells are also referred to as haploid, meaning there is only one copy of the genome.
How many chromosomes are in a human somatic cell?
A human somatic cell has 23 pairs of chromosomes; 46 total.
How many chromosomes are in a human gamete?
A human gamete has 23 chromosomes - half of the number in a somatic cell. A gamete only has one copy of each chromosome, instead of two like a somatic cell.
Describe how the sex chromosomes in a human differ from the other chromosomes.
The sex chromosomes are the chromosomes that determine the biological sex of mammals at birth. Unlike the other 23 pairs of chromosomes, the sex chromosomes are not identical. One, called the X chromosome is much larger than the other, which is called the Y chromosome. The combination of X and Y determines whether an organism will be biologically male or female. XX gives a female, XY gives a male.
Describe what a gene is.
A gene is a section of DNA coding for a trait. For example, the gene for eye colour is a section of DNA which determines the eye colour of the organism. The sequence of bases in the gene give the instructions to produce the trait.
Explain why the sequence of bases is important for a gene.
A gene carries the instructions for producing a particular trait. The sequence of bases in a gene is important because a different order of bases can result in a different trait. Think of this kind of like using a recipe to bake a cake - you have to mix together your dry ingredients with the wet, put it into the cake pan, and then put it into the oven. You need to follow the steps in the recipe in the right order, or you will get a different product - if you put the dry ingredients straight in the oven and then try adding the wet ingredients at the end, you certainly won’t get a cake! A gene is similar - the order of the bases is important, but in the case of a gene, we are making a protein (not a cake). Different sequence of bases, different protein.
Define the term allele.
An allele is one version of a gene. For example, we may have a gene for eye colour. This gene gives the instructions to make coloured eyes. The gene can come in two or more different versions, called alleles. One allele might encode blue eyes, while another encodes brown eyes. In both cases, the gene still gives the instructions for eye colour, just different eye colours in each case.
Explain what a trait is.
A trait is a physical characteristic which can be observed, such as eye colour.
Explain what the word heritable means.
“Heritable” means a trait or mutation can be inherited. That is, passed down from parent to offspring.
