Unit 6 Lesson 2: Genes, Chromosomes, and DNA Flashcards
What is DNA
a nucleic acid molecule that contains genes
Where is DNA located
DNA (deoxyribonucleic acid) is a long nucleic acid molecule found in the nucleus of a cell.
What does DNA contain (hint: think about protein)
It contains the coded genetic information for making proteins.
What is a gene
a section of a DNA molecule that codes for a protein. A gene is a segment of a DNA molecule that contains the information needed to make a specific protein.
What is DNA is wrapped around with
DNA is wrapped around histone proteins
DNA is wrapped around histone proteins and packaged into a compact structure called a
chromosome
What is a chromosome
a thread-like structure in the cell nucleus that contains DNA wrapped around proteins called histones
How many genes can one chromsome contain
One chromosome can contain thousands of genes along its length.
How amny chromosomes do humans usally have
Humans usually have 23 pairs of chromosomes.
Do al species ahve the same amount of chromosomes
The number of chromosomes in different species vary and can be used to identify the species.
Chromosomes in cats vs fruit fly
For example, cats usually have 19 pairs of chromosomes, whereas a fruit fly usually has only 4 pairs.
Do all of the same specioes organims ahve the same amount of chromosomes
There are times when an organism may have one or two extra chromosomes, or be missing one or two chromosomes in a cell.
variance in the number of chromosomes in a cell is known as
chromosomal aneuploidy.
Give an example of chromosomal aneuploidy in humans
For example, instead of a human cell having 46 chromosomes, the cell may have 45 or 47.
What is DNA sometimes called a double helix
The DNA molecule is sometimes called a double helix because its structure resembles a twisted ladder or zipper.
How amny sides or backbones does DNA have and waht is it held together by
. Like a ladder or zipper, DNA has two sides, often called backbones, which are held together by cross-pieces or rungs.
phosphate group –
a chemical group that consists of phosphorus and sulfur that links the backbone of DNA together
deoxyribose
a sugar that forms the backbone of a DNA molecule
nitrogenous base
a part of the nucleotide that contains carbon rings with nitrogen, oxygen, and hydrogen; there are four nitrogenous bases: adenine, thymine, guanine, and cytosine
What do the backbones of DNA consist of
The backbones consist of alternating phosphate groups and molecules of the sugar deoxyribose.
What does each rung of DNA contain
Each rung contains a pair of nitrogenous bases—adenine, thymine, cytosine, and guanine, which are bonded together in specific pairings.
What are the specifc pairting of nitrogenous bases
. Adenine always pairs with thymine, and cytosine always pairs with guanine.
How many genes might a segment of DNA have
. The segment of DNA that makes up a single gene may have between one hundred and two million bases.
What determines the structe of a protein in DNA
The sequence of bases within the gene contains the code that determines the structure of a protein.
Prokaryotic cells vs eukaryotic cells
Prokaryotic cells do not contain a nucleus, but eukaryotic cells do. eukaryote – a type of cell that contains membrane-bound organelles like a nucleus. prokaryote – a type of cell that does not contain membrane-bound organelles
prokaryotes vs eukaryotes in the process of DNA are the same or different
prokaryotes and eukaryotes package their DNA very differently.
- How is DNA packed into chromosomes in eukaryotic cells
In order to pack DNA into chromosomes and chromosomes into eukaryotic cells, the DNA molecule is tightly wrapped around a type of protein called a histone.
2 What is a nucleosome in the second step of DNA in eukaryotic cells
Each intertwined DNA-histone complex is then coiled into a bead-like structure called a nucleosome.
What does nuclesome mean and how is it formed?
a bead-like structure formed when DNA is wrapped around a single group of histone proteins in eukaryotes.
3 in eukaryotic cells what are chromatin and what do they do to nucleosomes
Nucleosomes are packed together to form rope-like structures called chromatin.
4 what is chromatin further condesned into
The chromatin is further condensed to form the X-shaped chromosome that most people associate with chromosomes.
When are X-shaped chromosomes formed
It is important to understand that these familiar X-shaped chromosomes only form during cell division.
Why are chromosomes typically not visvile in the nucleus as saperate chromosomes
Chromosomes are loose chromatin when the cell is not dividing, so they are not typically visible in the nucleus as separate chromosomes.
Prokaryotic cells are very different from eukaryotic cells in how they handle their DNA. ELaborate; describe the diference in chromsomes
First, prokaryotic cells typically only have a single chromosome, and this chromosome is circular instead of linear as in eukaryotes.
Prokaryotic cells are very different from eukaryotic cells in how they handle their DNA. ELaborate; describe the diference in the size of chromosomes
Second, all prokaryotic chromosomes are small compared to the chromosomes of eukaryotes.
Why dont prokaryotes need histones
. Because of these differences, prokaryotes do not need histones in order to package their chromosome into the cell
Do prokaryotes ahve to condense the chromosomes like Eukaryotes?
They also do not need to condense the chromosomes before cell division as much as eukaryotes do.
As stated previously, humans usually have twenty-three pairs of chromosomes. What do 22 of these pairs do
Twenty-two pairs of these chromosomes carry genes that code for the proteins body tissues need in order to function.
What does the 23rd pair of chromosomes contain
The 23rd pair of chromosomes contains genes that code for sex characteristics.
In mant cases the 23rd pair contains..
In many cases, the 23rd pair contains one X chromosome and one Y chromosome.
What is the X chromosome realted to
The X chromosome carries female traits, including those associated with reproductive, physical, and physiological processes.
Y vs X chromsome in terms of size
The Y chromosome is smaller than the X chromosome by a third
What does the Y chromosome carry
carries male traits, including those associated with reproductive, physical, and physiological processes.
Who does the XY sec determination system apply to
This is known as the XY sex determination system, and it is used by humans, most mammals, and some insects.
What is XX associated with and what is XY associated with
In this system, XX is associated with females and XY is associated with males.
There are not always 2 chromosomes in the 23rd pair. Why is that?
Since chromosomal aneuploidy occurs when cells divide, a different number of chromosomes can occur in a sex cell or somatic cell.
Chromosomal aneuploidy in sex cells results in 5 known combinations, described as follows:
- XO: a chromosome is missing, and one X- Chromosome chromosome is present.
- XXX: an additional X chromosome is present in the XX combination.
- XXY: an additional X chromosome is present in the XY combination.
- XYY: an additional Y chromosome is present in the XY combination.
- XXYY: an additional set of XY chromosomes is present in the XY combination.
Chromosomal aneuploidy in sex cells results in 5 known combinations. How often do these occruances occur
Incidences of these occurrences can range from 1 in 400 (0.25%) to 1 in 2,000 (0.05%) of the population, depending on the type of chromosomal aneuploidy.
THe tow mebers of a chromosome pair are identical or not identical?
The two members of a chromosome pair may or may not be identical. They have the same genes, but the genes may be somewhat different.
The two members of a chromosome pair may or may not be identical. They have the same genes, but the genes may be somewhat different. Give an example with freckells
For example, consider the gene that codes for the trait of the presence of freckles in humans. One chromosome in a pair may have a gene that carries the code for freckles, whereas the same gene on the other chromosome in the pair might not carry the code for freckles.
What are alleles
Some traits can be expressed if only one copy of a gene version is present. Other traits require two identical versions if the trait is to be expressed. These different versions of the same gene are known as alleles.
What was it like whent he earth first formed
When the earth was first formed, it had a plethora of inorganic molecules, molecules that are not found in living things. However, there were no organic molecules, molecules that contain carbon and are found in living things.
When and who devloeped the Oparin-Haldane Hypothesis
The Oparin-Haldane hypothesis resulted from the work of two scientists in the 1920s, Aleksandr Oparin and John Haldane.
What did Aleksandr Oparin and John Haldane beilive about the fromation of organic molecules
They believed that organic molecules were formed from the inorganic molecules present on earth.
How could inorganic molecules turn into organic molecules
This could have been the result of inorganic molecules reacting with each other to form organic molecules. They could have received the energy needed for this reaction from ultraviolet (UV) rays from the sun and/or from lightning.
monomer
building block of large molecules
polymer
a large molecule made up of multiple monomers
How would the devleopment of inorgnaic molecules ot organic molecules be like
Inorganic molecules could have reacted to first form monomers, small building blocks, such as nucleotides or amino acids which would then come together to form larger polymers, such as nucleic acids (RNA and DNA) and proteins.
What dies expereiments such as the the Miller-Urey experiment tell us about the Oparin-Haldane Hypothesis
These experiments have proven that in many different types of conditions, inorganic molecules can react on their own, with minimal help from scientists, to form organic molecules.
What was the first nucelic acid to form according to theOparin-Haldane Hypothesis
The RNA world hypothesis suggests that RNA was the first nucleic acid to form, and DNA resulted from two RNA strands attaching to each other.
Wha tis the Meteorite Hypothesis
The meteorite hypothesis suggests that organic molecules made their way to earth from space.
What have sceicnesits find in space that supports the Metorite hypothesis
Scientists have found that the ingredients necessary to create organic molecules can be found in space and, in fact, organic molecules themselves have been found in space
What bolsters the theroy that billions of yeats ago metories brought the first organic molecules ot earth
Meteorites that have recently fallen to earth have been examined. Organic molecules and structures were identified on these meteorites
What information do genes contain?
Genes contain the information needed to make proteins.
Explain the structure of a DNA molecule.
A DNA molecule looks like a ladder that has been twisted. The rails of the ladder are made of deoxyribose (a sugar) molecules and phosphate groups. The rungs of the ladder are comprised of four nitrogenous bases: adenine, guanine, cytosine, and thymine. In DNA, adenine and thymine are always paired together. Guanine and cytosine are always paired together.
Describe what determines the shape of a protein and explain why the shape of a protein is important.
The shape of a protein is determined by the sequence of amino acids, and the sequence of amino acids is determined by the sequence of bases on the DNA. The shape of a protein determines what molecules it interacts with and how it interacts with those molecules. This is vital to the function of the protein.
What is the relationship among DNA, genes, and chromosomes?
A molecule of DNA is made up of segments called genes. DNA is packed inside structures called chromosomes.
Compare and contrast the DNA of prokaryotes with the DNA of eukaryotes.
Prokaryotic DNA typically comes in one circular chromosome while eukaryotic DNA comes in many linear chromosomes. Eukaryotic DNA tends to be much larger and requires proteins called histones to package properly.
Describe the two hypotheses about the origin of DNA.
The Oparin-Haldane hypothesis says that inorganic molecules reacted to create organic molecules such as nucleotides. These bonded together to form RNA and DNA. The meteorite hypothesis says that organic molecules such as DNA first came to the earth on a meteorite from space.
Look at the photograph of the black and orange calico cat. What evidence can you use to determine the sex of the cat without doing a physical exam or genetic testing?
The cat has orange coloring, white coloring, and dark coloring. I know that male cats with the genes for this coloring rarely live, have health problems if they do, and are usually sterile. So, this cat is probably female.
What role do genes play in determining the structure of proteins?
The sequences of the bases in the genes of the DNA molecule determine the structure of the proteins. The sequences of the bases in the DNA determines the sequence of amino acids in the protein.
Explain the effects of a chromosomal mutation that deletes part of the chromosome.
Since chromosomes contain genes and genes contain sequences of DNA that code for proteins, you would expect a deletion of part of a chromosome to also prevent the cell from producing certain proteins. The severity of this deletion depends upon the importance of the proteins that were deleted.
What evidence is there to the claim that the structure of a protein is determined by a gene?
DNA contains the codes that determine the structure of proteins. Each gene codes for one protein. If there is an error in the base sequence of a gene, a defective protein—or no protein at all—will be made.
You are given a section of a DNA molecule. You are told that the bases are this order: AAATTTCCCGGG. How can you predict what the order of bases on the other half of the molecule will be?
In the DNA molecule, adenine is always paired with thymine, and cytosine is always paired with guanine. Therefore, the sequence of the other half of the DNA would be TTTAAAGGGCCC.
