8.1.6 Chromosomes

Chromosomes

8.1.6

Objectives

Learners can:

• describe the structure and function of chromosomes

• explain the role of chromosomes in heredity and genetic diversity

• cell

• chromosome

• DNA

• gene

• mutation

Prerequisite Vocab

• karyotype

New Vocab

Vocabulary

a visual display of an organism's chromosomes

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Karyotype

Match

Match the vocabulary word to its definition.

• mutation

• DNA

• cell

• chromosome

• gene

change in an organism's DNA

carries information about any organism

basic unit of living things

structure that contains DNA

segment of DNA that codes for a trait

• change in an organism's DNA

• carries information about any organism

• basic unit of living things

• structure that contains DNA

• segment of DNA that codes for a trait

Chromosome Basics

Each species of plant and animal has its characteristic number of chromosomes. Sometimes, these chromosomes are carried in body cells, which make up parts of the body like bones and muscles or leaves and stems. Cells contain 2 copies of each chromosome, one from each parent.

Humans have 46 chromosomes (23 pairs)

Humans

Dogs have 78 chromosomes (39 pairs)

Dogs

Corn has 20 chromosomes (10 pairs)

Corn

Fruit flies only have 8 chromosomes (4 pairs) and they are popular for research because of their short life span.

Fruit Fly

DNA

Each chromosome carries one DNA molecule. A gene represents a segment of DNA. Scientists estimate that humans have 20,000 to 30,000 different genes. Chromosomes carrying DNA are found in just about every cell of the body. However, because cells are constantly dividing and being replaced by newer cells, it is essential that the genetic information is properly reproduced in the newly formed cells.

The two sugar-phosphate backbones of a DNA molecule are connected by one of four nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides will always match up the same way with adenine pairing with thymine and guanine pairing with cytosine.

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Nucleotides

The DNA uncoils.

Step 1

The DNA molecules split apart, which results in 2 single strands.

​​Step 2

Free nucleotides are attached to their matching pairs on the single strand.

​​Step 3

2 identical DNA molecules result and then are re-coiled into a new chromosome.

​​Step 4

​DNA Replication Process

Multiple Choice

Following DNA replication, the two arms of a replicated chromosome are _____.

• identical to each other

• almost the same as each other

• about half the same and half different

• exact opposites of each other

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Types of Genetic Disorders

Down Syndrome results from an extra 21st chromosome. This can cause a change in body and brain development.

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Down Syndrome (Trisomy 21)

There are 2 chromosomes that present with abnormalities. They are different lengths from one another and can lead to leukemia.

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Philadelphia Syndrome

Open Ended

Take a look at the website. Choose 1 genetic disorder and share the following information:

disorder name

the gene/chromosome affected (the cause)

2-3 characteristics of people with the disorder

treatment for that disorder (if included)

https://www.healthdirect.gov.au/genetic-disorders

Genetics Review