Science: Chromosomes, Genes, and DNA

This set of flashcards covers cellular genetics, inheritance patterns, species variation, and basic processes of the carbon cycle based on lecture notes.

Where are chromosomes found and what is their composition?

Chromosomes are found in the nucleus of the cell and are made of DNA and protein.

When do chromosomes become visible?

Chromosomes become visible only during cell division.

How many chromosomes are in humans and mango trees?

Humans have $46$ chromosomes ($23$ pairs) and mango trees have $40$ chromosomes.

How are genes defined?

Genes are small segments of DNA arranged along chromosomes, serving as the basic physical and functional units of heredity.

What are examples of traits influenced by genes and the environment?

Examples include climate adaptation, skin colour change from sun exposure, and larger lungs in people living at high altitudes.

Describe the components of a DNA molecule.

DNA is made of a sugar-phosphate backbone and chemical bases: $Adenine (A)$, $Thymine (T)$, $Cytosine (C)$, and $Guanine (G)$.

How do the chemical bases pair in DNA?

$Adenine (A)$ pairs only with $Thymine (T)$, and $Cytosine (C)$ pairs only with $Guanine (G)$.

What are the main functions of DNA?

The functions of DNA are to store all genetic code, build proteins, and control cell activities.

Which gender is associated with $XX$ and $XY$ chromosomes?

Females are $XX$ and males are $XY$.

How is the sex of a baby determined according to the notes?

The sperm decides the sex; if the sperm carries an $X$, the baby is female ($XX$), and if it carries a $Y$, the baby is male ($XY$).

Compare the number of chromosomes in gametes versus the set after fertilisation.

Gametes have only $23$ chromosomes, and fertilisation restores the full set of $46$.

What is the definition of a species?

A species is a group of organisms that can reproduce together to produce fertile offspring.

What are the two causes of variation within species?

Variation is caused by genetics (such as blood groups and fingerprints) and the combination of genes and the environment (such as height and different flower colours).

What are the functions of leaf stomata?

Stomata allow gas exchange (letting $CO_2$ in and $O_2$ out) and control water.

What are the main processes of the carbon cycle?

The main processes are photosynthesis, respiration, decomposition, and burning/combustion.

List the carbon compounds mentioned in the notes.

Carbon compounds include carbohydrates, proteins, fats and oils, and fossil fuels.