Genetics Lesson 6 - Part 1 and 2

Genetics Lesson 6

How did the boys get the mutation that results in DMD?

Learning Goal: I can understand the role of DNA and chromosomes in passing traits from one generation to the next.

Open Ended

What do you know about genes so far?

Open Ended

In your own words, what is a gene?

Multiple Choice

True or false: Genes literally make things like eyeballs, personality, and other body parts.

• True

• False

Multiple Select

Genes are...(hint: there's more than 1 correct answer)

• made of DNA

• instructions to make certain proteins

• made of RNA

• all the same length of DNA bases (letters - A, T, C, G)

• different lengths of DNA bases (letters - A, T, C, G)

Multiple Choice

True or false: The length and sequence of the gene relates to the size and shape of the protein. (Bigger the gene, the larger the amount of amino acids, and the bigger the protein)

• True

• False

What are genes?

• Genes are segments of DNA that code for the production of specific proteins. 

• The code of DNA is made up of four nucleotides that are named for the unique base making them up:

• * adenine (A) * thymine (T) * guanine (G) * cytosine (C) 

• These four specific building blocks make up the “letters” of the DNA alphabet. The order of DNA nucleotides is important for the production of a functional protein.

What are alleles?

• Each cell actually contains two copies of each gene - one from each parent.

• The copies could be identical or they could be different versions of the same gene, called alleles.

Genes and Alleles

• You inherit 1 of each type of chromosome from each parent (23 pairs for a total of 46)

• Each chromosome has genes in it

• Alleles are the versions of genes

• Some alleles are the same and some alleles are different

• In this image, there are 2 different alleles for the E gene (E and e)

Genes and Alleles

• On these two chromosomes are 3 different genes (A, B, and G)

• There are two versions of each gene

• A gene: A and a; B gene = B and b; G gene = G + G

• Both the A and B gene have different alleles (uppercase and lower case, a + A, B +b)

• The G gene has two of the same alleles (G + G)

Multiple Choice

How many genes do these chromosomes each have?

• 6

• 2

• 12

• 8

Multiple Choice

Look at gene A. Do these chromosomes have the same alleles for gene A?

• Yes

• No

Multiple Choice

Look at gene B. Do these chromosomes have the same alleles for gene B?

• Yes

• No

Multiple Select

Look at gene E. What are the alleles for gene E? (Select up to 2)

• Dark Blue

• Purple

• Brown

• Green

• Light blue

Open Ended

In your own words, what is the difference between a gene and an allele?

How many genes do humans have?

• A genome is all of the genetic material in an individual cell of an organism. 

• All cells in that organism contain the same genome. (Your brain cells, heart cells, liver cells, skin cells, etc all have the same genome!)

• It is estimated that the human genome contains about 20,000 genes. Out of these 20,000 genes, over 100,000 different proteins can be made!

How many genes do humans have?

• Coding regions in genes can be recombined with different segments to code for different proteins

• There are over 6 billion nucleotides in the human genome, yet only 1.5% of those nucleotides actually code for proteins. 

• The remaining 98% of nucleotides in the genome does not code for proteins.

• Some of the sequences in this portion of the genome work to turn genes “on or off.” That is, they control whether certain proteins are made or not.

Open Ended

What is something you learned about genes since the start of this lesson?

What are chromosomes?

• Chromosomes are structures located inside the nucleus of animal and plant cells.

• Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA), which is condensed and folded around the protein.

• You can also think of a chromosome as the set of alleles an organism inherits from its parents.

What are chromosomes?

• DNA is tightly wrapped around spool-like proteins, called histones. Without such packaging, DNA molecules would be too long to fit inside cells.

• For example, if all of the DNA molecules in a single human cell were unwound from their histones and placed end-to-end, they would stretch 6 feet.

What do chromosomes do?

• For an organism to grow and function properly, cells must constantly divide to produce new cells to replace old, worn-out cells.

• During cell division, it is essential that DNA remains intact and evenly distributed among cells.

• Chromosomes are a key part of the process that ensures DNA is accurately copied and distributed in the vast majority of cell divisions.

• mistakes do occur on rare occasions.

What do chromosomes do?

• It is also important that reproductive cells, such as eggs and sperm, contain the right number of chromosomes and that those chromosomes have the correct structure.

• If not, the resulting offspring may fail to develop properly.

• For example, people with Down syndrome have three copies of chromosome 21, instead of the two copies found in other people.

Poll

Does the number of chromosomes relate to how complex an organism is?

• Yes

• No

• Maybe

How many chromosomes do humans have?

• Humans have 23 pairs of chromosomes, for a total of 46 chromosomes (23 pairs x 2). 

• each species of plants and animals has a set number of chromosomes.

• There is a species of protist (Oxytricha trifallax) with over 15,600 chromosomes!

https://www.nationalgeographic.com/science/phenomena/2013/02/06/you-have-46-chromsomes-this-pond-creature-has-15600/

Multiple Choice

True or false: All living things have chromosomes.

• True

• False

Multiple Choice

How many total chromosomes do humans have?

• 23

• 46

• 48

• 24

Open Ended

In your own words, what are chromosomes and why are they important?

Do all living things have the same type of chromosomes?

• Chromosomes vary in number and shape among living things.

• Most bacteria have one or two circular chromosomes.

• Humans, along with other animals and plants, have linear chromosomes that are arranged in pairs within the nucleus of the cell

• The only human cells that do not contain pairs of chromosomes are reproductive cells, or gametes, which carry just one copy of each chromosome.

Human karyotype

Open Ended

What do you know about how chromosomes are inherited (or passed down from one generation to the next)?

How are chromosomes inherited?

• In humans and most other complex organisms, one copy of each chromosome is inherited from the female parent and the other from the male parent.

• This explains why children inherit some of their traits from their mother and others from their father.

How are chromosomes inherited?

• The only human cells that do not contain pairs of chromosomes are reproductive cells, or gametes, which carry just one copy of each chromosome.

• When two reproductive cells unite (fertilization) they become a single cell that contains two copies of each chromosome (zygote).

• This cell then divides and its successors divide numerous times, eventually producing a mature individual with a full set of paired chromosomes in virtually all of its cells.

Do males have different chromosomes than females?

• Females have two X chromosomes in their cells

• males have one X and one Y chromosome

Multiple Choice

True or false: Humans all have the exact same type of chromosomes.

• True

• False

Multiple Choice

Which type of sex chromosomes do males typically have?

• XX

• XY

• WX

• WZ

Multiple Choice

Which type of sex chromosomes do females typically have?

• XX

• XY

• WX

• WZ

Multiple Choice

How many chromosomes do sex cells (sperm and eggs) have?

• 23

• 46

• 12

• 24

Open Ended

Why do sex cells (sperm and eggs) have 1/2 the amount of chromosomes that body cells have? (23 in sex cells, 46 in body cells)