Unit 6 Lesson 2: Genes, Chromosomes, and DNA

Question 1

What is DNA

Answer 1

a nucleic acid molecule that contains genes

Question 2

Where is DNA located

Answer 2

DNA (deoxyribonucleic acid) is a long nucleic acid molecule found in the nucleus of a cell.

Question 3

What does DNA contain (hint: think about protein)

Answer 3

It contains the coded genetic information for making proteins.

Question 4

What is a gene

Answer 4

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.

Question 5

What is DNA is wrapped around with

Answer 5

DNA is wrapped around histone proteins

Question 6

DNA is wrapped around histone proteins and packaged into a compact structure called a

Answer 6

chromosome

Question 7

What is a chromosome

Answer 7

a thread-like structure in the cell nucleus that contains DNA wrapped around proteins called histones

Question 8

How many genes can one chromsome contain

Answer 8

One chromosome can contain thousands of genes along its length.

Question 9

How amny chromosomes do humans usally have

Answer 9

Humans usually have 23 pairs of chromosomes.

Question 10

Do al species ahve the same amount of chromosomes

Answer 10

The number of chromosomes in different species vary and can be used to identify the species.

Question 11

Chromosomes in cats vs fruit fly

Answer 11

For example, cats usually have 19 pairs of chromosomes, whereas a fruit fly usually has only 4 pairs.

Question 12

Do all of the same specioes organims ahve the same amount of chromosomes

Answer 12

There are times when an organism may have one or two extra chromosomes, or be missing one or two chromosomes in a cell.

Question 13

variance in the number of chromosomes in a cell is known as

Answer 13

chromosomal aneuploidy.

Question 14

Give an example of chromosomal aneuploidy in humans

Answer 14

For example, instead of a human cell having 46 chromosomes, the cell may have 45 or 47.

Question 15

What is DNA sometimes called a double helix

Answer 15

The DNA molecule is sometimes called a double helix because its structure resembles a twisted ladder or zipper.

Question 16

How amny sides or backbones does DNA have and waht is it held together by

Answer 16

. Like a ladder or zipper, DNA has two sides, often called backbones, which are held together by cross-pieces or rungs.

Question 17

phosphate group –

Answer 17

a chemical group that consists of phosphorus and sulfur that links the backbone of DNA together

Question 18

deoxyribose

Answer 18

a sugar that forms the backbone of a DNA molecule

Question 19

nitrogenous base

Answer 19

a part of the nucleotide that contains carbon rings with nitrogen, oxygen, and hydrogen; there are four nitrogenous bases: adenine, thymine, guanine, and cytosine

Question 20

What do the backbones of DNA consist of

Answer 20

The backbones consist of alternating phosphate groups and molecules of the sugar deoxyribose.

Question 21

What does each rung of DNA contain

Answer 21

Each rung contains a pair of nitrogenous bases—adenine, thymine, cytosine, and guanine, which are bonded together in specific pairings.

Question 22

What are the specifc pairting of nitrogenous bases

Answer 22

. Adenine always pairs with thymine, and cytosine always pairs with guanine.

Question 23

How many genes might a segment of DNA have

Answer 23

. The segment of DNA that makes up a single gene may have between one hundred and two million bases.

Question 24

What determines the structe of a protein in DNA

Answer 24

The sequence of bases within the gene contains the code that determines the structure of a protein.

Question 25

Prokaryotic cells vs eukaryotic cells

Answer 25

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

Question 26

prokaryotes vs eukaryotes in the process of DNA are the same or different

Answer 26

prokaryotes and eukaryotes package their DNA very differently.

Question 27

1. How is DNA packed into chromosomes in eukaryotic cells

Answer 27

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.

Question 28

2 What is a nucleosome in the second step of DNA in eukaryotic cells

Answer 28

Each intertwined DNA-histone complex is then coiled into a bead-like structure called a nucleosome.

Question 29

What does nuclesome mean and how is it formed?

Answer 29

a bead-like structure formed when DNA is wrapped around a single group of histone proteins in eukaryotes.

Question 30

3 in eukaryotic cells what are chromatin and what do they do to nucleosomes

Answer 30

Nucleosomes are packed together to form rope-like structures called chromatin.

Question 31

4 what is chromatin further condesned into

Answer 31

The chromatin is further condensed to form the X-shaped chromosome that most people associate with chromosomes.

Question 32

When are X-shaped chromosomes formed

Answer 32

It is important to understand that these familiar X-shaped chromosomes only form during cell division.

Question 33

Why are chromosomes typically not visvile in the nucleus as saperate chromosomes

Answer 33

Chromosomes are loose chromatin when the cell is not dividing, so they are not typically visible in the nucleus as separate chromosomes.

Question 34

Prokaryotic cells are very different from eukaryotic cells in how they handle their DNA. ELaborate; describe the diference in chromsomes

Answer 34

First, prokaryotic cells typically only have a single chromosome, and this chromosome is circular instead of linear as in eukaryotes.

Question 35

Prokaryotic cells are very different from eukaryotic cells in how they handle their DNA. ELaborate; describe the diference in the size of chromosomes

Answer 35

Second, all prokaryotic chromosomes are small compared to the chromosomes of eukaryotes.

Question 36

Why dont prokaryotes need histones

Answer 36

. Because of these differences, prokaryotes do not need histones in order to package their chromosome into the cell

Question 37

Do prokaryotes ahve to condense the chromosomes like Eukaryotes?

Answer 37

They also do not need to condense the chromosomes before cell division as much as eukaryotes do.

Question 38

As stated previously, humans usually have twenty-three pairs of chromosomes. What do 22 of these pairs do

Answer 38

Twenty-two pairs of these chromosomes carry genes that code for the proteins body tissues need in order to function.

Question 39

What does the 23rd pair of chromosomes contain

Answer 39

The 23rd pair of chromosomes contains genes that code for sex characteristics.

Question 40

In mant cases the 23rd pair contains..

Answer 40

In many cases, the 23rd pair contains one X chromosome and one Y chromosome.

Question 41

What is the X chromosome realted to

Answer 41

The X chromosome carries female traits, including those associated with reproductive, physical, and physiological processes.

Question 42

Y vs X chromsome in terms of size

Answer 42

The Y chromosome is smaller than the X chromosome by a third

Question 43

What does the Y chromosome carry

Answer 43

carries male traits, including those associated with reproductive, physical, and physiological processes.

Question 44

Who does the XY sec determination system apply to

Answer 44

This is known as the XY sex determination system, and it is used by humans, most mammals, and some insects.

Question 45

What is XX associated with and what is XY associated with

Answer 45

In this system, XX is associated with females and XY is associated with males.

Question 46

There are not always 2 chromosomes in the 23rd pair. Why is that?

Answer 46

Since chromosomal aneuploidy occurs when cells divide, a different number of chromosomes can occur in a sex cell or somatic cell.

Question 47

Chromosomal aneuploidy in sex cells results in 5 known combinations, described as follows:

Answer 47

* 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.

Question 48

Chromosomal aneuploidy in sex cells results in 5 known combinations. How often do these occruances occur

Answer 48

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.

Question 49

THe tow mebers of a chromosome pair are identical or not identical?

Answer 49

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.

Question 50

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

Answer 50

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.

Question 51

What are alleles

Answer 51

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.

Question 52

What was it like whent he earth first formed

Answer 52

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.

Question 53

When and who devloeped the Oparin-Haldane Hypothesis

Answer 53

The Oparin-Haldane hypothesis resulted from the work of two scientists in the 1920s, Aleksandr Oparin and John Haldane.

Question 54

What did Aleksandr Oparin and John Haldane beilive about the fromation of organic molecules

Answer 54

They believed that organic molecules were formed from the inorganic molecules present on earth.

Question 55

How could inorganic molecules turn into organic molecules

Answer 55

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.

Question 56

monomer

Answer 56

building block of large molecules

Question 57

polymer

Answer 57

a large molecule made up of multiple monomers

Question 58

How would the devleopment of inorgnaic molecules ot organic molecules be like

Answer 58

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.

Question 59

What dies expereiments such as the the Miller-Urey experiment tell us about the Oparin-Haldane Hypothesis

Answer 59

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.

Question 60

What was the first nucelic acid to form according to theOparin-Haldane Hypothesis

Answer 60

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.

Question 61

Wha tis the Meteorite Hypothesis

Answer 61

The meteorite hypothesis suggests that organic molecules made their way to earth from space.

Question 62

What have sceicnesits find in space that supports the Metorite hypothesis

Answer 62

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

Question 63

What bolsters the theroy that billions of yeats ago metories brought the first organic molecules ot earth

Answer 63

Meteorites that have recently fallen to earth have been examined. Organic molecules and structures were identified on these meteorites

Question 64

What information do genes contain?

Answer 64

Genes contain the information needed to make proteins.

Question 65

Explain the structure of a DNA molecule.

Answer 65

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.

Question 66

Describe what determines the shape of a protein and explain why the shape of a protein is important.

Answer 66

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.

Question 67

What is the relationship among DNA, genes, and chromosomes?

Answer 67

A molecule of DNA is made up of segments called genes. DNA is packed inside structures called chromosomes.

Question 68

Compare and contrast the DNA of prokaryotes with the DNA of eukaryotes.

Answer 68

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.

Question 69

Describe the two hypotheses about the origin of DNA.

Answer 69

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.

Question 70

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?

Answer 70

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.

Question 71

What role do genes play in determining the structure of proteins?

Answer 71

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.

Question 72

Explain the effects of a chromosomal mutation that deletes part of the chromosome.

Answer 72

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.

Question 73

What evidence is there to the claim that the structure of a protein is determined by a gene?

Answer 73

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.

Question 74

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?

Answer 74

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.